I'm not a big fan of T-Mobile, but it depends on your needs. They have great service where they have coverage but their coverage area isn't very big. It sucked being the only person in a group with no service in many areas while I had T-Mob. Also, don't jump at the new phone on the block, let it age a little and you'll probably be able to get it free after rebate within a couple months. Check out T-Mob's very accurate coverage map, it goes into very fine detail and can show if the service will work for you where you need it.
Scott