Here's the long and short of it: if you've got T-Mobile's $50 Simple Choice plan, your LTE data and tethering buckets will double in size from 500MB to 1GB (at no extra cost, mind you) starting on March 23. If you're more of a power user, you can shell out an additional $10 per month per line to bring those buckets up to 3GB a pop, and a new $30/month option grants you unlimited LTE data speeds and 5GB of tethering. This does come at a price though: the $20/month tier that gave you unlimited LTE data and 2.5GB of tethering has been rejiggered to provide 5GB of each. Sure, 5GB is a lot of data, but it doesn't hold a candle to what you used to get. Thankfully, if you've already got that plan, it's yours to keep.
But really, it's T-Mobile's aggressive (and surprising) stance on international data and messaging that really helped to turn some heads. As you might expect, the carrier's global data roaming footprint has just grown (if only by a bit): you'll be able to check emails and fire off messages with impunity in Afghanistan, Guam, Honduras, Macao, Uganda, the Canary Islands and San Marino. The biggest get here though is the inclusion of unlimited international messaging for--you guessed it--a whopping $0 extra per month. It's probably not going to spell the end for hugely-popular messaging apps like Whatsapp, but smoothing out wrinkles of international texting couldn't hurt T-Mobile's reputation. As usual, you don't have to do anything to claim these goodies -- they'll just show up on your bill, waiting oh-so-eagerly for you to use them.