The new Optimus V looks like pretty much the best deal in the country for a smartphone right now, but I did see people complaining about losing their data connection when the phone idled.
I'm on T-Mobile prepaid for ~$25 a month because I already had a gsm phone (iPhone) but otherwise I'd probably switch.
Goodbye $70+ AT&T bills.
Plans are pretty good (although you do pay for every minute), phones leave a lot to be desired since they are basically unsubsidized and they are aimed at teenage texters.
They seem to have the best (cheapest) hassle-free plan with pretty good phones.