I was really impressed, and so where all the others with me on a trip to Ecuador this last week. Mine was the only one that worked. The hotel tried to work with cingular on the phone, to get the others to work. No avail. While AT&T rates for roam are steep, the alternative is to get an unlocked phone and buy a local pay as you go sim. I keep an unlocked Razor to do just this on longer trips. This approach is not necessarily cheaper if you do not plan upon returning or end up not using it up. I have resorted to giving sims with time left to my drivers for a tip.
Most companies will unlock your phone, upon request, after you have had the phone for 90 days. It may take them some time to actually come through on the request, but they do. Personally, I just buy the phones, unlocked, to start with.
Ultimately, AT&T will be put into a position to unlock the phone, since you purchased it outright and not as a freebie for a contract. While the iPhone is expensive, there is still a bit of subsidy going on.