Lots of bug fixes and improvements, and some new features as well. Here are some highlights:
New: New "Last Filter" item under the Filter menu. New Layer With Selection / New Layer With Selection via Cut. Holding down the option key when choosing a core image filter from the Filter menu, now applies it right away without bringing up the filter panel. Acorn can now open and save JPEG 2000 images. New Overlay blend mode. New "Offset" filter under Filter->Tile Effect. Smarter trim command, now crops to the edge color and not just alpha pixels. Fancy Crop (tm). The crop tool now tries to figure out a nice default if you just click on the canvas without dragging. (Ok, not really (tm)). Holding down the option key when using Trim to Edges works just like Fancy Crop (tm!) does.
Fixes/Changes: Tweaked the way selections work, so they more closely resemble "industry standards". Much better looking cursor for the draw tool. Plugged some memory leaks. Various performance improvements when opening large files. The canvas no longer accepts "first clicks" when it's not part of the main window. QuickLook fixes, and more.
The full release notes are available as well.