I am interested in the answer to this question as well. I have heard many say that American is behind in terms of cell phone network standards and rates poorly in terms of cell network offerings. I am not sure if any GSM phone will work in the USA( at least for a reasonable price and service ). The cell industry in US is in need of regulation and standardization, but given the current state of the FCC I doubt that is happening anytime soon. There is also the 3G standard, that from what I know is limited to EU zone.
http://en.wikipedia.org/wiki/3G The economics of the cell phone industry are quite complex. Compatibilities and standards are rolled into service fees. It seems like the cell world is frantically holding back the changes that recent technology have made possible.
BTW- what happened to the Tempe municipal wireless project?
-jmz