To whoever stumbles upon this thread: version 1.2.1 is now out (now live at revisionsapp.com and mac app store version in review) and introduces the following two main new features

- Ignoring certain files and folders based on regular expression match (note: premium-only feature)

- Ability to launch any diff app (including Apple FileMerge), by calling a custom AppleScript script (this also gets around the restrictions imposed by the app sandbox). Sample script for FileMerge provided.

Correcting my earlier post, actually TextWrangler (one of the natively supported diff apps) is free of charge, and now with the custom diff script users can connect to other free diff apps as well (such as FileMerge).

Will soon be adding the possibility to purchase Premium functionality outside the Mac App Store, probably within a week or so.