If you are looking for value, take a look at T-Mobile. They have great speeds IF you are in a metro that has good 3G coverage, and the price is great. I have been with them for 7 years and the customer service is unmatched. They were actually rated #1 in customer service by someone...JD Power or something....look it up if you care, lol.
The coverage is no where near Verizon, who's customer service is hell...but I think the big picture looks promising in the near future with T-Mobile rolling out their HSPA+ network this year. It's already in the Philly area, and they have been building up for this for the last few years with plans to roll out 100 major metros by the end of the year.
They have been behind the others, but I would look for that to change in the future.