I was a happy Virgin Mobile USA customer for a long time (6 years!), paying a real $27/mo for 300 minutes and unlimited text/data. However, their selection of Android phones kind of sucks, and Sprint doesn't do rural coverage around here (but it covers my home great), and my data speeds sucked (occasionally unable even to stream audio at 64kbits/s), and Virgin Mobile announced that if I got a new phone they would force me to switch to a $35/mo ($37?) plan, and they had started to spam me with text messages (though sparingly, on the order of once a month).
So when my LG Optimus V died (it spent a whole day in my pocket during a heavy rainstorm, destroying its SD card reader in a severe way), I decided to jump from Virgin Mobile and get a Nexus 4. That's GSM-only, so T-Mobile or AT&T. I was leaning towards one of the cheaper T-Mobile MVNOs (around $30/mo), but I learned that T-Mobile has a $30/mo plan that they hide by only offering it at Walmart, which is 100 minutes and 5GB data (or something). Perfect.
The T-Mobile experience sucked a *bunch* and I left it after one month (unfortunately, not before paying for two months). Everything they did was so astoundingly bad, and reflects a company with unsound management. Here's a list, roughly sorted in the degree to which it angered me:
In other words, I could not reliably receive phonecalls, could not receive text messages at all, they spammed me constantly, and every single element of their support aparatus was a fucking nightmare.
Oh, on the plus side, 5GB is more data than I'd use in a year, and it was super fast (on the order of 10Mbits/s).
So I switched to Airvoice Wireless (AT&T MVNO), which is $40/mo for unlimited minutes and 500MB data. It is a little more expensive, but they ported my number in mere minutes (and text messages already work!), I will probably never see another "no service" alert for the rest of my life, they haven't spammed me yet, and their webpage completely satisfied all of my needs without any difficulty (though it is an absurdly minimalist website).
UPDATE Sep 27, 2013: Have still not seen "no service" since switching to Airvoice! Have not received *any* spam from them! And they already doubled my monthly data to 1GB!
UPDATE June 20, 2014: Have now seen "no service" three times -- in BFE -- not bad! Still no spam!
It is just shocking to me how much T-Mobile sucks, and how unforced their errors are. Anyone who cites T-Mobile as an element to competition in the wireless spectrum is full of shit. Anyone who is a T-Mobile customer is probably an idiot.
The FEC/DOC/SEC/etc should just let AT&T buy up T-Mobile already and put it out of my misery.