I rented Bullet Witch the other day and managed to play through one and a half levels before something came up and I had to stop for a while.
After said while I came back to play and the disk wouldn't load. I looked and it and it was scratched quite severely.
I'm suprised it loaded up the first time. And I'm pretty sure it wasn't my 360 that caused it. So it was screwed to begin with.
And just died after I played. Somewhat of a shame.

The game was very, very mediocre but it had it's moments.
I liked the designs of the broom weapons and though somewhat unwieldy the magic was impressive to look at.

My brothers gone out and is going to get our money back along with my next rental - Iron Man.
I played the Iron Man demo and as with Bullet Witch, well it was mediocre.
But I'm not buying the thing or anything, so mediocres just fine. All it has to do is keep me busy a couple of days until Saints Row 2 comes out.
I haven't quite finished Brothers in Arms yet and it's a great game but it's pretty much all I've played since I bought it so I feel like mixing it up a tad, hence the rentals.

I usually don't rent game. I usually buy or nothing.
Definetely a bad habit. It's how you wind up with games like Superman Returns on your shelf.
That said the majority of my buys are solid, I've only got a couple of stinkers.