Next time you log into Xbox Live, you'll be prompted to accept an update. Exciting stuff, eh?
Not so much. You can poke around your 360 all you like, but you won't find it doing anything it didn't do before. Zip, zero, nada, a great big pile of steaming nowt. Unless, at the same time as you grabbed the update, you hit your 360 with a brick...
Or... you can travel into the future!
Larry 'Major Nelson' Hryb, Microsoft's online mascot, tells us, "This update contains code to ‘prepare for future growth of the service.’" That is all.
Which brings us to the subject of the Spring update. Except... that it doesn't, really. Because Hryb ain't saying squat about that, either. "At this point we have nothing to announce, and the moment there is information to share I will do so", he tells us.
Source: Major Nelson