My humble observations on what DF needs in Windows 7 to make an already rock solid program perfect:
Look and feel of Windows 7 including 'squarish' buttons and matching transparancy.
Window buttons pulled off main monitor taskbar when they're on the second monitor.
Clock & date on the right end of DF's bar.
Thumb/previews that match the look of Windows 7 previews.
The other taskbar program some of us have seen (that is in early pre-beta and is simply just a taskbar) already has these things going for it, so it seems reasonably do-able.
It seems to me that Windows 7 (especially RC) came on us in a rush, is solid (and nearly final), so there is a mad rush by developers, that would have normally waited until the final product is out, to tackle these issues.
Jon's progress seems to be methodical and very practical: getting the whole program honed to perfection before adding the extras. Other, simpler programs may have rushed in and gotten the look down already, but they will spend the coming months getting all the bugs out and still not have the fullness, utility and usefulness of DF.