Martin O'Donnell pointed out this Wireless Week article that reports T-Mobile USA has added over 3.2 million subscribers in the last nine months, a 24-percent increase in their customer base. Revenue for the third quarter was $2.46 billion or about $55 per customer. This has had a very positive impact on parent company Deutsche Telekom's earnings.
At one point, it looked like Telekom had overpaid to acquire VoiceStream, the company now called T-Mobile USA. I'm not hearing too much mention of that now.
I like T-Mobile because their wireless data service rates are among the cheapest around. This makes them the carrier of choice if you use a Treo 600, a BlackBerry 7230, or an exclusive on their network like the T-Mobile Sidekick II.