I use Sprint and am happy with it. I use it alot for work (get to expense it) so I pay $100 a month for 2000 anytime minutes, unlimited nights and weekends, and a second line (two phones sharing the plan)
DH has the second phone on this agreement, our calls to each other don't count towards the minutes so we generally use our cell phones over the home phone to talk to each other/DS, etc.
We also get unlimited nights and weekends and free long distance and dropped our home long distance service (actually, we have 50 minutes free long distance each month on our home phone with this cell phone agreement with Sprint, but we never use it)
I also like that Sprint just added a new thing (recently) where existing customers get the same sales and new customers. If your phone is 18 months old or older you can get the same rebates/specials as new service agreements. DH's phone is my old phone (3 years old and a few functions aren't working) so we're going to replace that one soon - will be able to replace mine after another 6 months or so, but doesn't need it.
They have a lot of different plan options and as I travel around the US for work, I like the wide network - rarely am I ever in "roaming" or no service.