we had such a thing that year, at the first day of the season a friend of mine overshot it throwing a back, landed flat on his feet and broke his back partially. luckily hes not paralyzed and is ripping again since march!
well its kinda funny, better than water ramps (i havent been to one i have to admit) is, i guess, that you can carve into the lip, since its just snow like on any other obstacle that you would throw the trick.
i wasnt too much into inverts before that year, but now i got backs, flat 5s,7s and misties 5s and 7s pretty much down. other people on the hill are now throwing switch backies, lincolns, lincoln 180s and other serious stuff just within a few days of learning and perfectioning, its good for getting used to the rotation.
but crashing on it isnt too nice as well as landing switch and doing switch backs afterwards of the bag, but all in all i would consider it "safe".
a guy said, that way over 1000 people hit the bag at our mountain (mostly gapers and racers, tourists who hit it straight) with like 10 injuries, thats a good quote i would say.