Do you think the 2.2 update for htc desire is as good as the iOS4 update for iPhone?
Are you joking? In terms of OS, everything I saw about iOS4 is just playing catch up to what other OS's already offer and have been offering for years.
Take multitasking, probably the biggest change for the iPhone in terms of usefulness and one of the main limiting factors for them to date - I've been able to do that properly (not the limited version Apple offer) on Symbian for at least 6 years, on Android since its inception.
There's loads of functionality available already on Android that Apple still haven't caught up with even in iOS4, let alone waiting for the 2.2 release (I won't repeat it all, it's already listed in this thread ad nauseam)
What Apple will be able to offer is integration with some of the services and apps that can now start taking advantage of this, their bookstore etc which inarguably will have a slick and easy to use front end. We should have a Kindle app coming to Android shortly, but Kindle's interface is unlikely to be as slick. Whilst I was able to edit video several years ago on my trusty N95, the iMovie app will undoubtedly be easier to use than this was.
However, if it delivers everything it should, 2.2 will give the Desire a huge boost and take it even further ahead of the iPhone in terms of functionality.
I think the only part Android is behind on is 'cohesiveness' (almost invetiably given Apple's control freak approach) and the services available from third parties. I'm happy to sacrifice the a little of the former for the sake of a more open platform (and it's not as though Android isn't cohesive, just not as much as Apple). As far as services go, we can only watch and hope that third parties continue to make the shift towards Android or at least supporting both platforms equally. The wind certainly seems to be heading in that direction as the sheer number of Android users grows and demands market attention.
iOS4 is pretty much an irrelevance in this debate though - it's just Apple playing catch-up with the rest of the world but selling it as something new and exciting.