Yep, have used them here in Miami Florida since February. Service is good. A lot of people complain about it though.
They don't really have much support, it is almost impossible to actually speak to a human being if you call them. On occasion I will get dropped calls, and sometimes it just doesn't work for a few minutes. But which other cellular providers don't have the same problems?
You have to pay extra to get a paper bill, so I just have the bill paid automatically with a credit card. The service area is limited. I don't travel much so it doesn't bother me. Long distance is .05 per minute, but you have to open a credit line first, same thing for roaming, you have to pay with a c.c. You also can't get internet access with their phones.
You get used to not worrying about minutes real fast! I had a friend of mine at the office crying that her Verizon bill was over $400 for one month. Yeah she talks a lot (and has a contract). I don't have to worry with mine. I probably use it anywhere from 1 hour to 3 hours per day, so I can't really complain.
What is amazing is the amount of people here in South Florida that have switched to them. Just about everywhere you go, you see their phone. I used to go and pay the bill in person since it was convenient for me (on the way home). But they have too much traffic at their store to do that now. They usually have a sign on the door that says they are out of phones for the day by 11 am. A lot of my friends have switched to them that still have contracts on their old phones; they just leave a message on their old line saying to call the new number and they pay both bills; it's still cheaper for them.
I imagine that one day they will be bought out by their competiton, but as you know, with most electronics stuff, things change rather quickly. Look at AT&T, they have the same plan nationwide but for $99. I really hope MetroPCS can keep this deal for a long time, but the big boys have to be hurting - I was with Sprint for years and switched as soon as they came here.