I have roamed in several European countries with my Vodafone (UK) card. It isnt cheap but it is probably comparable to the deals people are finding on the web. When I put it in my phone in the US it shows that it is working. I havent tried using it for voice. I sent my self a couple text messages. Still waiting for them to arrive. It might not work in the US. But I have used it no problem in France, Italy and Spain.

Well the sms I sent with my prepaid Vodafone UK SIM card from here in SAN worked when sent to my TMobile US postpaid account. So apparently you can use Vodafone prepaid cards in the US. Interestingly, the SMS I sent to my Verizon wireless phone hasnt come through yet. I will try again later. I entered the number manually, perhaps it had a mistake.