As it stands, T-Mobile currently sells three smartphones that'll support its nascent LTE network. The first two are the Galaxy Note II and the Lumia 810 -- both of which must receive a software update to enable the functionality. We recently spoke with T-Mobile about the matter, and while representatives confirmed the pair would be updated, the company isn't ready to discuss a timeline. The third smartphone that's known to support LTE over Band 4 (1700MHz AWS) is the Nexus 4, and while it's completely possible to enable this dormant feature, the phone has yet to receive FCC certification for this purpose. We're cautiously hopeful that the Nexus 4 will be certified for LTE Band 4, but until this happens, operation in this mode is illegal and comes at your own risk.
Beyond this trio, T-Mobile has revealed two forthcoming smartphones that'll support its flavor of LTE: the BlackBerry Z10 and a revised Galaxy S III. Both devices will offer LTE connectivity out of the box, but T-Mobile has yet to nail down a specific release date for either handset. In the case of the BlackBerry Z10, it won't hit store shelves until mid-March at the very earliest.
All things told, the Galaxy Note II, Lumia 810 and Nexus 4 are each worthwhile purchases. If you're looking to buy a T-Mobile smartphone today, we recommend you choose among these three. If you're less than thrilled with the bunch (and you're willing to wait), the BlackBerry Z10 or the retooled Galaxy S III each merit consideration. Beyond that, we've no doubt that T-Mobile has many other juicy, LTE-enabled smartphones in the pipeline. Just remember to shop smart, folks.
Update: As of the Android 4.2.2 release, the ability to enable LTE support for the Nexus 4 has been disabled. We'll be monitoring whether workaround methods to re-enable this functionality become available.
Update 2: On April 1st, T-Mobile revealed that the Lumia 810 won't receive a software update to enable its LTE capabilities.