Acorn 5.1.1 October 14, 2015.
New Stuff Fixed Stuff
Acorn 5.1 September 29, 2015.
New Stuff Scripting Stuff Fixed Stuff
Acorn 5.0.1 September 2nd, 2015.
Fixed Stuff
Acorn 5 August 20th, 2015.
The Big New Things in Acorn 5:

The Shape Processor.
Acorn has a really great new feature called "Shape Processing". Have you ever wanted to generate a bunch of new shapes, and then arrange them all in a circle and adjust that radius right on the canvas? What about taking all your shapes and re-ordering them from smallest to largest? What if you wanted to take all your shapes and randomly assign each one a new color, and then scatter them around the canvas in a billion different locations? What about pushing all the shapes on your layer out of the way of a giant circle?

Well, now you can.

Shape Processors are filters for shape layers, which will move and tweak and generate and adjust shapes for you. And best of all, they are non-destructive and stackable (just like Acorn's filters). So you can add a bunch, tweak, save, close, and come back later if you change your mind.

Things that go snap.
This is a lot more snapping going on now. Snap to Grid, guides, shapes in layers, other layers, selections, canvas bounds, etc. It was a complete rewrite, there are now global preferences available for fine tuning how you'd like it to work, and we even made those changeable per document.

Completely rewritten bitmap selection stuff.
It's super accurate and works wonders with retina displays.

Non destructive Levels and Curves.
Levels and Curves joins all the other non destructive filters- this is pretty awesome. You can use Levels and Curves on shape layers, even combine in the same filters list, tweaking both at the same time, and add a Curves filter multiple times to the same image. I have no idea why you'd do this, but it sounds fun.

PDF Import.
When you open up a PDF, you can now choose the resolution, page, and background color of the PDF you are opening.

Crop tool improvements.
Pressing 'x' will now swap the aspect ratio of the current crop frame (if you have one that is, otherwise it'll swap the current back and foreground colors).
Pressing 'h' will toggle hiding the areas outside of your crop frame.
You can now rotate your image while making a crop.

Hundreds of minor bug fixes.
Yes, we are really going to list this in the "big new things" section.
We fixed hundreds of minor bugs. Bugs that built up over the years that very few people ever encountered, like "the shortcut key for zooming in doesn't work when the keyboard layout is set to Dvorak - Qwerty ⌘". So we fixed pretty much all of those. It took months and months of work, it was super boring and mind numbing and it was really hard to justify, and it made Acorn 5 super late. But we did it anyway, because something in us felt that software quality has been going downhill in general, and we sure as heck weren't going to let that happen to Acorn. So we took a long break from adding features and just fixed stuff.
And if you reported one of these bugs that was fixed in Acorn 5 and we haven't already sent you a license- let us know and we'll make you one. (See, another good reason to report any bugs you find- free stuff!).

More shape layer and bezier stuff.
New menu items - "Shape ▸ Bezier Stuff ▸ Align Anchors to Pixels" and "Align Anchors to Half Pixels" (the latter command shows up when you hold down the option key). This will align all the anchor points in your shape to the pixel grid (or half of it). This helps with making crisp lines for you bezier nuts out there.
You can now change the inner radius of star shapes. THIS IS AWESOME. It's actually quite flexible, and you can make some really neat star shapes (and did you know- you can change the number of points on your star using the View ▸ Quick Config popover?).
New option to reset bezier control points under the Shape ▸ Bezier Stuff menu
If you double click on an open bezier shape, it will signal to the shape that you would like to continue extending it. There's also the option to do this under the Shape ▸ Bezier Stuff menu item.
You can temporarily toggle the "snap to pixels" setting when moving a bezier anchor by holding down the control key while moving it with the mouse.
You can now invert the selection on shape layers.
The Shape Quick Config popover will now work when you don't have any shapes selected (and the settings you change will reflect on the next shape you make).
The contextual menu for the layers list has a new "Rasterize Shape Layer" menu for use on shape layers.
You can now close a path when creating it by pressing the enter or return keys. Pressing the escape key will finish editing it as well, but keep it open.
You can now move multiple selected anchors in a bezier path with the arrow keys or mouse.
If you have the option "auto select layers" turned off, a single click and drag in a shape layer will now move all the graphics without them needing to be selected first.
If you have a single text box selected and you press the enter key, Acorn will start editing it.
Holding the command key over a control point for resizing shapes will allow you to rotate it instead. I'm thinking of killing off the secret rotate handles outside shapes as well. Does anyone care?
Added Control-C as a way to select a color. This is awesome if you want to pick up on another color, but you're currently editing text and the 'i' key doesn't cut it.
Changed the modifier to move selected shapes by a half pixel to shift-option (from command-option).
New shortcuts to toggle the fill / stroke on selected shapes. Shift-F for fill, Shift-B for stroke.

New blend modes.
Acorn now has a "Pin Light" blend mode, as well as a "Mask" blend mode. The Mask one is pretty awesome- it works just like a layer mask, white lets pixels through, black erases.

Support for Photoshop brushes!
There's approximately 10 billion PS brushes available for download on the internet, and you can drag and drop one onto Acorn to import and make new brushes.

Speaking of brushes…
The Brush tool has now been renamed to the Paint tool. Because a bunch of other tools now use brushes, and it hopefully reduces confusion.
About those other changes I just mentioned. The clone, paint, smudge, dodge, burn, and other tools that had crappy brushes now each have their own unique brush that you can configure via the brush designer. So now you can have scatter for the clone tool. Or adjust flow and softness for the burn tool. Or turn pressure sensitivity on and off for the eraser. Etc.

Image metadata editing (aka, EXIF and IPTC, sitting in a tree).
Image metadata is now viewable and editable. Use the File ▸ File Info… menu item to bring up the editor. While not everything is editable, lots of good things are. And this is new- so if there's something you'd like to see here, let us know!

New options in the Filter Palette having to do with selections:.
"Blend with canvas selection", which is the old standard behavior when applying filters to the selection. Acorn will apply your filter(s) to the currently selected area in your bitmap, and then draw the results of that filter over your layer.
"Copy over canvas selection". This option will apply your filters to the current selection, and then replace the pixels in your selected area with the results of the filter. So in this case, if the filter returns transparent pixels, your layer will become transparent in those areas.
"Ignore canvas selection". This option will ignore the canvas selection, and work copy the result on top of your whole layer.

Miscellaneous new stuff.

Changed Stuff
Acorn 4.5.6 September 29, 2015.
Fixed Stuff
Acorn 4.5.5 June 15, 2015.
New Stuff Fixed Stuff

Acorn 4.5.4 January 30th, 2015.
Fixed Stuff

Acorn 4.5.3 January 7th, 2015.
Changed Stuff Fixed Stuff

Acorn 4.5.2 November 18, 2014.

Acorn 4.5.1 September 3rd, 2014.

Experimental Stuff
Acorn 4.5 July 28th, 2014.
Acorn 4.4 May 26th, 2014.
Acorn 4.3.1 February 24th, 2014.
Acorn 4.2.3 January 4th, 2014.
Acorn 4.2.2 Dec 10, 2013.
Acorn 4.2.1 Dec 8, 2013.
Acorn 4.2 Dec 6, 2013.
New Stuff:
Bug Fixes:
Acorn 4.1.1 September 18th, 2013.
Acorn 4.1 August 12th, 2013.
Acorn 4.0.5 June 20th, 2013.
Acorn 4.0.4 May 21, 2013.
Acorn 4.0.3 May 7, 2013.
Acorn 4.0.2 May 2nd, 2013.
Acorn 4 May 2nd, 2013.

Tools get their own palette now.
It was getting cramped in there, so we broke out the tool icons into their own palette. In addition we updated a bunch of icons and made everything look better in general.

Layer styles and Filters sitting in a tree…
We rolled the layer styles and filters interface into a single non-modal window. This also means that filters are non destructive! You can still chain together filters like before, but now you can undo and redo your adjustments and even save them as part of your Acorn file. In addition to the filter settings being in a non modal window- you can now directly modify filter parameters right on the layer by dragging any little circles that show up when the filter window is present! (And if you'd like the previous filter window back for some reason- we're keeping it around for a little while- just hold down the option and command keys when choosing your filter from the Filters menu.)

The one exception where the filters window isn't modal (and is destructive) is when you are using a filter on a selection.

Curves Adjustments (finally!)
Acorn now has a Curves Adjustment tool, which you can get to from the Image ▸ Curves… menu. To add a new point on a curve, click on the curve and start dragging. To remove a point on a curve, drag it either left or right until it's past the location of the next point on the curve.

Vector tool improvements.

Levels tool improvements.
The Levels window got a complete rewrite, with a gamma option (to control mid-tones) as well as an option to update the histogram live.

Speed improvements.
Compositing, filter previews, and everything in general is faster. Way faster Flood Fill, Magic Wand, and Instant Alpha tools. The Render Clouds filter got a little speed bump as well.

Multiple layer selection.
The layers list now allows you to select multiple layers. This means you can re-order, delete, move, or lock a bunch of layers at once.

Other great things worth mentioning.

Stuff for Scripters:

Acorn 3.5.1 January 22, 2013
Bug Fixes:
Acorn 3.5 October 9, 2012
New Stuff: Changes: New Stuff for Scripters: Lots of Important Fixes:
Acorn 3.3 July 15, 2012
Acorn 3.2.2 May 1, 2012 Acorn 3.2.1 February 16, 2012 Acorn 3.2 December 2, 2011 Acorn 3.1.2 October 11, 2011 Acorn 3.1.1 September 23, 2011 Acorn 3.1 September 19, 2011 Acorn 3.0.3 July 15, 2011 Acorn 3.0.2 May 31, 2011 Acorn 3.0.1 May 5th, 2011 Acorn 3.0 April 12th, 2011 Acorn 2.6.5 Acorn 2.6.4 Feb 4, 2011 Acorn 2.6.3 Jan 10, 2011 Acorn 2.6.2 October 29, 2010 Acorn 2.6.1 October 25, 2010 Acorn 2.6
October 21, 2010 Acorn 2.5.1
September 27, 2010 Acorn 2.5
September 16, 2010 Acorn 2.3.2
August 2, 2010 Acorn 2.3.1
May 17, 2010 Acorn 2.3
April 30, 2010 Acorn 2.2.2 Acorn 2.2.1 Acorn 2.2 Acorn 2.1 Acorn 2.0.3

Acorn 2.0.2

Acorn 2.0.1 Acorn 2.0 release notes:

The Big things: The WHOLE list, including bug fixes: Acorn 1.5.3 release notes: Acorn 1.5.2 release notes: Acorn 1.5.1 release notes:

Acorn 1.5 release notes:

New Features: Changes / Additions: Bug Fixes:
Version 1.2.1 Version 1.2 Version 1.1.1 Version 1.1 Version 1.0.3 Version 1.0.2 Version 1.0.1 Acorn 1.0
September 10, 2007.