This isn't necessarily sweeter than what you get on T-Mobile. While the magenta network's Data Stash lets you save data for up to a year, any untapped AT&T data disappears after that extra month -- you can't stockpile it for a Netflix marathon during the holidays. Still, this is a big deal if you're not clinging on to a grandfathered unlimited data plan for dear life. AT&T is no doubt hoping that this will entice you to stay on a more capacious tier than you really need, but it'll definitely make better use of the service you're paying for.

[Image credit: AP Photo/Mark Lennihan]