P1n3apqlExpr3ss: AT+T - 850/1900 UMTS
Verizon - CMDA/LTE
Sprint - They do appear to have a UMTS network but seem to be pushing 4G tech
T-Mobile - 1700/2100 UMTS
Best bet is easily AT+T but I heard the Prime will be Verizon exclusive?
The US versions will be, but there is apparently Asia and Europe versions coming too
The Unlocked event is now in Hong Kong
http://www.engadget.com/2011/10/11/samsung-and-googles-ice-cream-sandwich-nexus-prime-event-back/