I'm not sure why people subscribe to GSM here in the US in order to travel. It makes sense for business, sure. Who cares about $1000 roaming bills when your work is paying. But for personal use, it makes no sense to me that someone would pay $2/minute with their US phone to make overseas local calls (restaurant, taxi, whatever).
Here's what someone advised me to do years ago and what I've done since then. I keep an unlocked Motorola V60, bought in 2002. When I get to... wherever... I just find the local Vodafone/Telefonica/etc. store and buy a prepaid SIM card kit for around £10 or €25. Pop it in the phone and voila, local number. I then SMS the number to my family in case they need to get in touch with me while I'm over there. In the meantime, I have a local phone. It's great.
Thought I'd spread the word on this since a co-worker mentioned today that he might be switching to GSM so he has coverage in overseas. After hearing this idea, he thought it sounded better than paying roaming fees.