Pre ordered, but only had chance to play it 3 times so far. The only issue I had with the previous game was that the submissions were so hard to do or escape from. Now that they've been revamped, they're a lot less complicated to execute and therefore makes it so that the fight isn't practically over as soon as the opponent takes you to the floor. Also there's the option to simplify the grappling controls for beginners which I imagine is very useful.
In the career mode, you can now move weight classes just by getting a winning streak going, I think 4 or more wins and you get offered fights from other divisions as well as your own, so you're not limited to fighting the people in the same weight class over and over until you defend the title a few times. Some of the training in career mode takes some getting used to and I'm still working on it, but I think once I get the hang of them they'll pay off.
So far all I've done is career mode, so I cant rate the other game modes, but if career is anything to go by then the other modes will be awesome too and UFC 3 will be a game to keep you busy for quite a while.