Let me start with, it's a great game. One of the best I have on my PS3 and one of the greatest of 2010 at the moment.
The action is great and it has a unique style and difficulty. But both of those aren't for everyone.
The style is heavy on the demon and angel motive with a lot of over the top sexist poses and impossible action scenes thrown in. Though fun, some people might detest this.
One time you're fighting burning angels, the next you are ridding a bike on a missle flying into space! It's insane!
The combo system is near perfect. Since the game slowly forces you to master it. After finishing on Normal you'll have a general idea, after Hard you'll be really good, but after Inf.Climax you'll be great at it. Do note that the difficulty is indeed insane at some points, and I mean "Demon's Souls eat your heart out" insane.
Most people also complain about issues that came from the porting. Since the latest patch these things are almost not an issue anymore.
There is some slowdown when there are 10-20+ enemies on the screen, but the loadingtimes and screen-tearing are fixed mostly!
Try the demo on PSN to see if you like the style and the combatsystem. But I tend to just yell BUY IT. It's a great game!