The real question is the extent of Cingular's roaming agreements with T-Mobile and/or AT&T Wireless, both of which have GSM coverage deployed at various places in the U.S.

AT&T Wireless is also in the process of converting TDMA 850 over to GSM 850. This makes things confusing if you're an AT&T or Cingluar TDMA customer. On one hand, you could buy yourself one of these GAIT phones that tries to cover every spectrum and standard, but the phones are larger and klunkier.

I'll argue that the "right" answer is to get one of these new tri-band GSM phones that's biased in favor of U.S. rather than European frequencies. The phone I'm likely to get (once it's available without being locked to the AT&T network) is the Nokia 6200. It supports GSM at 850, 1800, and 1900MHz. That means you get one European band and two U.S. bands. You don't get GSM 900, which is the predominant non-US GSM frequency, but you're likely to get something when you're in Europe, and you do spend more of your time in the U.S.