Pros: Good price value, for individual and family plans, and solid service on all the basics.
Cons: Few cutting-edge options, one major issue with customer service.
Summary: My teenage daughter was using a prepaid phone, but once she hit high school, I realized I was paying $30 a month with very careful usage keeping it "Topped Up." For the same $30 added to my plan, she got unlimited MyFave minutes to the five numbers she calls most (I'm not one of them), plus unlimited weekends and nights, plus she and I split 700 "Anytime" minutes, all for a totall of $69.99 (I get my own five MyFave numbers). Calls within the carrier are not free, as with some services.
I did a lot of research before signing up. Other carriers were better for business use or for people who call a lot of different people (though T-Mobile wasn't bad), but T-Mobile was best for my type of usage, which I think is pretty basic. My cell phone is my home phone, but I don't use it for business, so most of my calls are to a handful of people, or else on weekends. Same with my daughter.
Now, their shortcomings. Their phones aren't really exciting. They have a few nice ones, and a lot of basic, mundane ones. You can get a great phone from them, but you won't have a lot of great phones to choose from. They are good on music phones, and middle of the road phones, and low-end smart phones, and budget phones with a good variety of options. They don't have the coolest GPS or camera or video phones. Their services lag behind other carriers, too. They don't have the 3G wireless Internet system, so if you use the Internet on the phone, it will be a little slower. They don't have wireless music or video downloads. They aren't stone age, but they aren't breaking down barriers. This is frustrating for a tech-nut like me, but I've got enough other gadgets that I don't mind. For some, though--say, a business traveller that wants everything to work through one device--this might kill the deal.
Last, customer service. The few questions I've had get answered quickly. Emailed help is slower than average, but I've never spent much time on hold on the phone, and they do seem to know I'm the customer and not a servant. Recently I had a problem, though. The phone I got for my daughter was defective, so they told me to send it back, but they charged me for the replacement phone they sent, promising to credit the old phone within 30 days of them getting it. This was almost enough to make me cancel service, but I wasn't sure other carriers handled it better, so I calmed down and did it. Not happy with that, as my ratings reflect. This could be a problem for people on the edge of their budget.
Hope that helps someone. I'd recommend them as a family carrier, and for their prices, and for the solid service they provide. For travelers or people who want the latest options, or who want all their cutting-edge tech needs rolled into one, maybe another service would work better. Again, T-Mobile isn't pre-historic, and they aren't a no-frills service. They have Internet, and some cool phones. They just aren't the best at it.