On the whole, it works about as well as I had hoped (+) but it has had a few notable glitches that annoy me.
1) There is no simple way to sync my google stuff (calendar, contacts, etc...) with my iPhone. The contacts got synced well enough, but while I was trying to use the Mobile Me app it nuked my contacts on google and I was never able to get it to sync the calendar (the contacts are still on my iPhone so I may be able to fix them, but it's annoying to say the least). iTunes also can't sync my Firefox bookmarks. To top it all off, it looks like I can only sync the iPhone to one computer at a time. I understand the logic to this given the RIAA's world view, but it's still stupid.
2) Having to use iTunes to "manage" my music etc... and put it on the iPhone. My Sansa View acts like a flash drive when you plug it in so managing music is just a drag and drop operation. Not so with the iPhone. Even on a reasonably good computer it tends to drag a bit and it's a bit of a drag to use.
3) No obvious way to remove apps from the iPhone. I'm sure there is a way, but given Apple's reputation as super-user-friendly, I was surprised that removing apps wasn't more straightforward.
4) Playing music works ok, but fiddling with the iPhone during playback is a bit more of a pain than it should be (IMO). I don't like having to access the slider after pushing the button. If I'm using it to play music while driving, it would be nice to just be able to click next without having to really "use" the iPhone. My Creative Nano and Sansa View Mp3 players are both easy to click forward and back without having to really "use" them.
5) The whole jailbreak thing. I shouldn't have to do this. I should be able to put whatever I want on the phone without it being an ordeal.
Now some things I like:
1) GPS and Google Maps, they rock, end of story. Plus it looks like there are some neat apps that can add location tags etc... to photos and I could use them to do some cool GPS stuff. Having access to that in the phone is awesome.
2) It's generally easy to use and works well. The device itself works quite nicely, it just has a few design decisions that annoy me. It would be nice to be able to customize some of the behavior/actions.
3) Battery life is pretty good (even w/ 3g enabled surprisingly). We'll see how it does once the battery starts to lose capacity over time, but right now I'm finding that it's lasting me just fine.
I'll probably have more thoughts on this later.