Well, yesterday we told your that the Mac App Store would be opening in 3 weeks. Will Apple tolerate significant interface changes in the App Store apps?
According the a review of the leaked Mac App Store requirements...they will be rejected.
6.1 Apps must comply with all terms and conditions explained in the Apple Macintosh Human Interface Guidelines
6.2 Apps that look similar to Apple Products or apps bundled on the Mac, including the Finder, iChat, iTunes, and Dashboard, will be rejected
6.3 Apps that do not use system provided items, such as buttons and icons, correctly and as described in the Apple Macintosh Human Interface Guidelines will be rejected
6.4 Apple and our customers place a high value on simple, refined, creative, well thought through interfaces. They take more work but are worth it. Apple sets a high bar. If your user interface is complex or less than very good it may be rejected
6.5 Apps that change the native user interface elements or behaviors of Mac OS X will be rejected