The major differences between 2.1 and 2.2 are the JIT and the ability to move apps (that explicitly allow it) to "external" storage (that is, the SD card). (Which brings up another point: prefer phones with more internal storage.)

My contacts and calendar are mostly on Google services, which get synced pretty much automatically. Contacts and calendars are both extensible, but I don't know for sure what extensions are available.

Bookmarks are a bigger problem. Largely I just don't worry about it. There are bookmark sync apps, though. I haven't tried any of them. I do all my desktop bookmarks syncing with Xmarks, but their Android client costs money, and I just don't care that much.

Oh, it's worth pointing out that you can get full refunds on App Market purchases for up to 24 hours after purchase.