So I got the game two days ago and I've been playing it for a while now. It's hella fun. It feels similar to MK9, yet different enough that I can like it (I dislike MK9). There's a nice variety of styles in the roster and the roster is pretty big, so I bet everyone will find one character to play. My favorite character is Solomon Grundy. He's a grappler and he's just the kind of character I love to play as in these kind of games; relatively slow but extremely powerful and mainly uses grabs. Hell, Grundy is now up there in my favorite fighting game grapplers list, along with UMvC3's Haggar and P4A's Kanji Tatsumi!
Every character has their own "gimmick" (character power) which is completely different for every one, and that adds some more variety to the roster (Flash slows down opponents by... becoming faster, Grundy has a chain of grabs which will buff him up in different ways, Superman has a temporary power up mode, etc).
The Super Moves which use all of your Meter are also really damn cool and extremely cinematic most of the time. Batman, for example, blinds you for a bit with some smoke and then calls up the Batmobile. While the batmobile arrives, he beats you up for a bit and then when the Batmobile is really close he does a really cool jump over the Batmobile and you get hit by the car. Superman punches you into space and then punches you back into the Earth. Grundy slashes you with a knife, then punches you into the air, jumps and then grabs you and throws into the ground and THEN he pulls his own grave from his stomach and slams it on your head! All of them are really cinematic, with great angles and graphics.
Each stage also has its own "hazards", which the players can use (even during combos) to deal even more damage against their opponents. Characters use them differently, too, depending on their type. Smart but "weak" ones like Batman will set explosives on cars, for example, while powerful beasts like Doomsday will just grab the car and throw it at their opponent. This adds further uniqueness to each character. There are also stage transitions, which deal a fair lot of damage and take the players to another part of the stage (and each part has its own unique hazards!). Learning how to properly use the hazards adds some depth.
I don't really know what else to say, I pretty much only talked about the things that I found to be pretty unique about the game, since I'm kinda tired. But yeah, I will say that the game is definitely awesome and that it's worth trying even if you dislike MK9 (cuz I dislike it and I love Injustice).