Straight up. Never had it freeze or crash or anything even once, so must be doing something right.
Also heard horizontal makes it more liable to scratch discs.
EDIT: Actually, a friend of mine had his uh.. Oblivion? Possibly, anyways, one of his discs had this perfect circle that was clearly visible and rather deep scratched into it. His 360 is horizontal. Though to be fair, it is modded. Yet another reason for me to not mod my 360, along with the obvious and the fact that his DVD drive broke as soon as he got back.