The device will sell for $679 with 64GB of internal storage. It supports LTE bands 4, 7 and 17, along with 3G UTMS bands 1, 2 and 5, and GSM frequecnies 800/900/1800/1900MHz. Its name, though, is Surface 2 (AT&T 4G LTE), which points to exactly which carrier will be officially supported. That being said, you should be able to get away with a T-Mobile USA SIM, as T-Mobile also uses LTE band 4 and 1900MHz 3G.
Despite the additional hardware, the Surface 2 with LTE promises the same battery life (up to 10 hours); it also basically weighs the same as the non-LTE model.
The Surface 2 (AT&T 4G LTE) reaches MicrosoftStore.com, retail Microsoft Stores, and Best Buy on Tuesday. For some reason, AT&T stores will not sell the device, though.
To be clear, this is the Windows RT-based Surface 2, and not the Windows 8 version.