T-Mobile is currently in the process of pushing a fairly major update to its version of the Galaxy S III, which brings Android 4.1.2 and a slew of new don't-call-it-Touchwiz features.
Auto-pairing via NFC
enhanced Camera options
Before grabbing this one, you'll need to be on build T999UVDLJC, have at least 50% battery, and not be rooted. If those bases are covered, you can either elect to pull the 168MB update over-the-air, or, for those who prefer the tethered-to-a-computer method, via Samsung Kies.