In reply to krank:
> if you dont believe me thats fine
I'm going to go out on a limb and say that no one has ever died at a CrossFit event from dropping a barbell on themselves.
Back to the OP, Rings are just apparatus. What you get from them depends on the exercise, but they can be difficult to use. Dips for example are considerably more difficult on rings than they are on static bars ( for obvious reasons, but you might be surprised just how much more difficult ).
As with any new technical exercise it's a good idea to get proper coaching, but assuming that you're not going to be attempting an Iron Cross, it's difficult to imagine how you could injure yourself with them.
Andrew.