I know 3 people with iPhones... One is a complete fanboy, so of course he wouldn't tell me if he ever had a problem, but I did laugh when he dropped it and cracked the screen.
The other two are girls who just bought it because it was the "in thing", neither of them are technical. One constantly complains about it freaking out and doing weird shit (in her words she hates it) and the other seems to have an iPhone (or maybe O2) induced text message delay. I've sat there next to her this week, both with a good signal and sent messages between my Nokia and her iPhone. Sometimes they arrive instantly, other times they take a few minutes. In one case a message took 2 hours, and sometimes they've just gone missing. Messages from her to me turn up pretty much as you'd expect, within a few seconds.
Now I don't know if this in a problem with the Orange/O2 interconnect or whatever, but until I proved this to her in person (and showed her my sent history) she thought I'd been ignoring her!
The iPhone is bad for your social life!
Sure the iPhone has a great interface, but I still don't trust the technical bit underneath it all. The half hearted attempt they made of implementing the SMS functionality in version 1 is enough to make me worry.