I'm not sure if you're kidding, so I'll bite:

- Frequently dropped calls - 3G connection problems - Delayed SMS and voicemails (sometimes by days) - App store problems - Short battery life

Some of these are AT&T's fault, no doubt. But I've had AT&T for the better part of a decade, and I've never had so many "network" problems as when I bought an iPhone. When your phone has dropped an important phone call with the CEO of a public company three times in 5 minutes in Central Park in New York City, it makes you want to break the piece of junk into a million pieces.

But the promise of the phone, and the experience when it does work, is really quite good. It's just not a piece of equipment you can rely on. I struggle with the thought of getting rid of it quite often, yet just can't seem to pull the trigger.

All of those apart from app store/battery are AT&T. None of those are issues in the UK with O2 as the carrier.

Battery life sucks if you leave 3G on, the app store is meh.

AT&T is a pretty well-publicized problem.

... In the US. Which is one country out of many.