I have T-Mobile and I have never had a problem with it.
I got a crappy phone one time and I took it back and the people at the store we so helpful and even the customer service i called were really friendly and i got a new phone in about 3 days with no charge!
the service around me house is great, and I even took it with me to arizona and i was amazed that it worked in the Grand canyon!
all of my friends didnt have service on their phones, but my T-mobile worked amazing!
the phone selection is probably my only complaint, since it sometimes slim pickings

overall, i love t-mobile. and it is so much cheaper and more quality as well as the best customer service