We at LetsRun use T-Mobile and love it. It's cheaper than Verizon and the CEO is a huge running fan.
It's coverage is fantastic in major cities. Now if you are going to be travelling a lot to say rural Oregon, it may not be for you.
Ours plans are very cheap but we are on the simple choice plans. It looks like they may only be offering unlimited plans now. Not sure if you can still sign up for simple choice or not. Unlimited for two lines is $120 per month (+ taxes and fees).
What we like about it is there are a) no overage fees b) you can use your phone free of charge to text/surf the Internet when overseas c) when overseas you can call for a reasonable race (20 or 25 cents per minute).
So every month, we know what we are going to be charged.
They also treat you like a human being. For example, they offered free calls in Brazil during the Olympics. During the Hurricane last week, they offered free calls to the Carribean so you could call loved ones. ON Tuesdays, they even give you a free gift (I got a free sub at Subway and a free pizza from Dominos).
Here's a true story. A rep from T-Mobile even called me (we have a busines account) to let me know that one of our lines was getting zero usage and did we want to cancel it. I couldn't believe it.
Great service.