[nerdtalker]

The US GSM model appears to trade WCDMA on Band 1 (2100 MHz) for Band 4 ("AWS" 1700 Tx/2100 Rx). Global GSM includes Band 1 since that's a very popular band internationally, but doesn't have Band 4.

Keep in mind, T-Mobile USA is predominantly Band 4 for WCDMA and LTE, and Band 2 (1900 MHz) with at most a single WCDMA carrier in markets for roaming, iPhones, and improved in-building coverage.

So no, it isn't useless to T-Mobile, and won't be limited to 2G speeds. There's no Band 1 (2100 MHz) deployed inside the USA. Band 4 tried to align itself with Band 1, but manages only to align some of the downlink (tower->handset) spectrum (2110 to 2170 MHz for B1, 2110 to 2155 for B4), the uplink/duplex spacing is entirely different (this is the 1700 MHz "band"), 400 MHz below downlink for B4 as opposed to 190 MHz below it for B1.

[wffurr]

Thank you for the thorough explanation. I see the difference now between full 2100 support and receive-only 2100 support.

A little disappointing, since I'm about to travel to the UK and Europe, and it would be awfully nice to have WCDMA everywhere. I guess that's another selling point for the Moto X, or I could just deal with T-Mobile's PCS support.