Which Cell phone operators have GSM?
 

I know Tmobile has fairly extensive GSM network. How do AT&T, Singular or Verizon compare with T-Mobile now?

Verizon has none and no plans for it. They and Sprint are committed to a different standard -- CDMA and its successors.

People here are more knowledgable than I, but I will provide my answer as I have researched this from a user's view point lately.

AT&T is rapidly building their GSM network out to replace the old TDMA system. They have a map on their attw.com website, their so-called Next Generation network. Compare it to the T-mobile map and they look comparable roughly although different in specific areas.

Cingular is building thier out too, again to replace TDMA.

How they compare depends upon where you are. I have had reasonably good experience with T-Mobile traveling around the U.S., and specifically a lot here in Northern Virginia.

I would say it has more dead spots than Verizon. I have used AT&Ts GSM and it was pretty good in Northern Virginia but not as good (IMHO) as T-Mobiles, but that probably depends upon where you go.

I believe that the carriers have some agreements in different areas to let competitors' customers seamlessly roam in those areas so you may end up using other networks without knowing it.

Selective cross roaming between GSM operators is occuring now (e.g. ATTWS allows you to roam on CERTAIN Cingular areas that ATTWS has no coverage). There is also joint network buildouts on interstate highways in the western US.

If you have a quad band GSM phone or a GSM850/1900 phone coverage will be less of an issue within the next year or so due to the presence of rural networks supporting GSM for roamers.