I've heard the anime is mediocre.
Report back when you're done, I might give it a watch.
It
IS.
Some of the story plays out a bit differently, but that didn't bother me.
My biggest complaints were:
#1. Bayonetta's personality isn't as fun to watch in the move
#2. The fights aren't as epic (especially the final battle).
#3. The characters look a little... off. The faces look a bit weird in certain shots and (i can't believe i as a man would say this)
Bayonetta's breast for example look way too big compared to her usual ingame appereance.
#4. Because of #1 and #2 the ingame cut-scenes were more entertaining than the movie.
Bayonetta (the game) doesn't take itself too serious, yet has many huge, epic, over-the-top-moments, and the heroine is just really fun, flashy, and enjoyable. For some reason they put a bigger focus on her being "mysterious" in the movie.
My girlfriend summed it up pretty nicely; "It's like the movie tried to make everything more dark and serious, but Bayonetta was all about being sexy, having fun and kicking a**."
Not a bad movie at all, but yeah, not that great either.
...buuuut i'd still advise you to give it a try. Maybe you'll get more enjoyment from it than most.