If you boot up you're Xbox 360 today, you'll be prompted to perform a system update. There are no new features in this update, however. "This update addresses interruption issues that some Xbox LIVE users may have experienced when playing a limited number of Xbox 360 games."
I hope the "limited number of Xbox 360 games" includes Fallout 3's "The Pitt" expansion as it has crashed on me numerous times.
There are no new features in this update. If you were experiencing problems with a game before patching and find your issue is resolved, please let us know in the comments section.