I found an article that says it has "100 new features" http://www.appleinsider.com/articles/09/03/17/iphone_3_0_100_new_features_for_users_1000_new_apis_for_devs.html but that's probably all marketing buzz, because the main one they're pushing is cut and paste (WinMo has been doing that for years anyway). And a landscape mode for notes.
Big deal, where's the multitasking? To be fair, they're also getting stereo bluetooth, but most mid-high end phones have that already. If they release new, better hardware then that could make a difference though.