Xbox 360 Problems

IGN has a decent article about the problems the 360 has had so far.

First they mention lockups/freezing.
If you have this problem, make sure your power supply brick is well ventilated.
If that doesn't cure the problem, call Microsoft at 1-800-4MXBOX. They'll help you determine if you have a hardware problem and take it from there.

There have also been problems with disk scratching.
What happens when you move your console from horizontal to vertical or vice versa while a game is spinning inside? Your game disk gets scratched, possibly to the point of being unusable.

The lights on the front of the console change when you change its position. Some gamers are probably showing off how the console knows its orientation while they forget they have a game inside, spinning at high rpm.

Though you may get a replacement copy of Perfect Dark Zero, chances are you won't get the exact game you scratched.

Lesson learned - don't move your console while a game is inside.

IGN Article