Acorn 3.3 is now available! It now features support for the new Retina MacBook Pros (via a "Retina Canvas"), Smart Layer Export (if you're a web or app designer, you'll love this), selection improvements, text improvements, and more. Check out the release notes for the full details.
If you purchased it through the App Store- don't worry Acorn 3.3 coming! Eventually. Acorn is still waiting in the queue down in Cupertino and it could either be a couple of days or even weeks till it's out (we submitted Acorn 3.3 on June 25th- and we've heard that sandboxed applications now take longer to go through the review process).
HOWEVER - if you've purchased Acorn through the App Store you can easily switch to the direct version just by downloading it off our website. Acorn will figure out that you've run the App Store version and automatically register itself.
Why didn't we wait till the App Store version was approved? With 10.8 coming out soon (Acorn 3.3 also includes Gatekeeper support) and the new Retina machines - we decided we wanted folks to get their hands on this sooner rather than later.
So grab Acorn 3.3, and have fun with it.