I'll second Cingular. Their reception is far better then T-Mobile. I can get uninterrupted GPRS data access from Colorado Springs to Dallas on Cingular, while a T-Mobile phone would struggle to even have signal for 50% of the trip. 850mhz support makes all the difference here in the US now.

However, keep in mind 900mhz is used over in Europe, and most tri-band phones that do 850 cut out 900. The phone would still work in Europe on 1800/1900mhz, but not as well if you get into a 900 area. I got the Razr not for the style, but because it is a quad band phone.

When I went to Europe, I had a T-Mobile phone. I told them ahead of time I'd be traveling there, and so they set my account to an international status to be able to roam onto the networks over there and have my phone number. It wasn't cheep though per minute, so I went with a prepaid SIM for my time instead. Ended up working out well.