I'm in a car on my way from Zurich to Davos happily blogging on my T-Mobile gprs connection that is roaming over Sunrize in Switzerland. When I landed, I had trouble connecting to Swisscom, but "611" and two rings later, I was connected to a friendly T-Mobile support person speaking in English and she gave me other roaming partners to try. Sunrize connected without a hitch. In Hawaii, Frankfurt, Helsinki and a little hiccup, but one call later in Switzerland, T-Mobile has consistently kept me connected. Also, the support people have been EXCELLENT and I haven't had to wait more than a few minutes on the phone.
I'm a happy camper and I'm SOO glad I didn't pick ATT.