Having played this a bit, and gotten over my old biases (a bit), I can give you some initial impressions.
It's actually fairly fun to play, once you learn how. The learning curve is ALL about learning how to parry. I played the console version quite a bit, and I probably lost my first five matches or so. Then I figured out the timing on parries, and the game got pretty easy, for the most part.
Played the Vita version for a while today, and had no problem using the parry system, and didn't lose a match or even come close to losing. Really, as long as you learn to parry, you've pretty much got the game down.
All that said, it can be surprisingly fun. It's not the least bit realistic in any way, which is kind of weird- it has MMA elements and moves, but they don't work like they would in real life- submissions just do "damage," there's no tapping out. The best strategy, in general, is to parry and then to throw a few strikes, and to clinch and strike from there if you can, since you're a lot less vulnerable to counters and parries from the clinch. And the AI parries a TON, so get used to that.
My biggest complaint with the game, by far, is that there's no career mode, and the story modes that are in the game are amazingly short. They take maybe 20-40 minutes per fighter, and they're all very easy, and they're all very similar. The ones for the women take 10 minutes max, as they're two fights, total. If there was a career mode that actually took more than 6-10 fights, it wouldn't be a bad game, really, since even though the gameplay is pretty basic, it's strangely enjoyable for some reason.
And the Vita version runs worse than the console versions for some reason. The models look about the same, but there's some pretty nasty hitching up on the framerate on certain moves and especially when you're in adrenaline mode and on the finishing blows.
Anyway, it's not as bad as I remembered it, but it really, really needs a longer career mode.
edit: one thing I just realized is that the movement system in the Vita version is vastly different (for the better) than the console versions. In the console versions, movement was completely bizarre, you had to hold down a button to walk perpendicular to your opponent rather than just away or toward. It eventually worked okay, but it was a bad system and was awkward. This version has a normal 3-D movement system like any other 3-D fighter would have and the game is much better off for it.
Thanks. There are no reviews for this game. Maybe one (user review) on Metacritic. I'll probably wait until this game goes down in price. From the looks of things, that doesn't look too far off. However, I'm not into MMA, so the differences between that and actual MMA don't really bother me. Once again, thanks.