Not bad... But not quite there....
The bad: Complicated controls for first time play. And when you punch some guy in the face, you don't get near the amount of satisfaction you get when you complete a game of minesweeper with only one square.
And combos are really hard to chain. Your character needs half a second to recover from his last move before he can dish out another. This is really frustrating in situations where you could just punch the guy there and knock him out, but no, your guy just had to rest and let the opponent see where your next punch comes from.
Also, when you try to escape or wrench a submission, you have to spin the analog nub like there's no tomorrow. And submissions take longer and longer when you work up the difficulty levels. Even when its spinning like a top, you still need to spin it at least 20 seconds before the guy submits.
But however, this game has a very nice presentation. Likenesses are captured really well, the ring is beautiful and animations are really well done. And the classic black and white slow-mo screen when you throw a good punch really adds on to the 'feel' and realism of the game.
The game is quite addictive and personally, I enjoyed it quite a lot and I'm sure many many others will too.