Your second point has some merit though: that once they gain significant market share in the U.S, T-mobile can become anti-customer. But T-mobile's prepaid plans and now this international texting gambit might force other carriers to follow suit before T-mobile gets to that significant market share. At that point T-mobile cannot afford to become anti-customer because other carriers would have started matching T-mobile's pro-customer offers in the meantime.
At least their competitors "get" more things better than them, so for the most part they're not even an option.
in the end, you end up with a result like in politics. Whoever has more money wins the whole market.
The market pretty much exchanged short term benefits (cheaper console, better phone plans) for worse longer term problems (lame games because you have no choice, more expensive phone plans because you have no choice)