ATT/Cingular are about 90% GSM now. T-Mobile is the other carrier with GSM service.
Verizon and print use CDMA technology and Nextel uses another proprietary technology.
So now your choise is down to 2 companies.
I think ATT/Cingular merger has created a much better coverage in GSM within the USA. T-Mobile's coverage is not as good (excluding major metropolitan areas).
So you have to see which company gives you the better deal and the phones you like once you determine which coverage is better for you. Check their coverage maps on line or in a store.
I was originally looking to see if I could use a couple of phones sold in Taiwan in the US. I was going to try and email the companies to find out, but I don't even know who provides GSM service. Verizon says they don't, I can't figure out how to contact AT&T, and I have to have an account to contact Cingular. Can anyone tell me who offers GSM service in the US?
And in case someone can tell me right off the bat, the two phones I'm wondering about is the ASUS J102 and Panasonic X200.