Oh boy... this question... I honestly, as everyone does, HOPE that MK9 will be good, but I have some serious concerns and doubts, but that doesn't mean that there aren't some things that I think look good.
First and foremost, I agree with Dreamcatcher, this game is going to be different than the former 2d games, and that's something we have to just deal with, OR go back to playing UMK3 and MK2.
I will say that the game looks a little too much like MKDC in terms of it's animation and gameplay so far. This isn't to say that they won't make the animation play like a 2d game, but if the animation is indicitive of anything, than we are dealing with more of the same in terms of MK9 and MKDC.
For the record, lets clear the air about MKDC... some people do like the game. I personally do not, and it has nothing to do with characters and such. It has to do with the inherent inequality in player properties from player 1 to player 2. P1 has a definitive advantage just by being P1, and that is inherently a broken quality that makes MKDC, in my opinion, nothing more that a flawed game with a flawed fighting system and ultimately nothing more than a casual game not worthy of any look into depth and strategy, as choosing P1 is all players' main priority(before winning the match). This is not the stuff that good games are made of.
With that said, I am praying that MK9 does not retain this property imbalance, because if it does, it will doom the game to the same level of casual play that plagued MKDC, with no real need to look further at any level of depth because of an inherently broken fighting engine. So far, I haven't seen any indication of this, which is good.
I do not like the idea that MKDC's U2 launcher could be a universal technique either. We've seen it from Scorpion so far, and definitely in Sektor's EX TP Uppercut, but what we don't know is if the EX actually includes the re-launch or if it's done manually. If it's manual, then Sektor has the U2 launcher as well and leads me to believe that it would be a universal technique. Lets hope not...
The game also has Throw Techs. I believe this to be a bad idea for MK in general. I never liked them in MK, though they work in SF. The problem is that in SF, there is no chip damage on normals when blocking. This means that you can't pressure in SF for chip damage unless you use a special or a throw. This leads to a close game coming down to throws and techs, and the occassional fake throw, punish the whiffed tech. All in all, throw techs will, in my opinion make this game more of a turtle fest than a rush down game... they make rushdown pointless because I'm not going to try to chip away when I can just go for the throw, especially since, in just about every fighting game, throws always beat normals...so if someone tries to tech while I'm chipping, I'll eat a throw. I expect the close game to come down to exactly that.. no chip, just throws attempts and techs.
Throw recovery/quick recover. I actually have no problem with this. It creates a good mixup and lets you choose, to a degree, how you get up. I don't necessarily like the idea of recovery attacks, so I hope they aren't in there. BTW, Throw recovery is different than a throw tech... it just lets you roll out of a throw.
EX move execution. I'm not keen on holding block to execute the EX moves. This means I can no longer buffer tap motion moves from block without the risk of executing the EX move instead of the normal move. The only way to fix this is to require the press of block while you press the attack... for instance, if I am buffering from block, I must actually release and re-press block with the attack for the EX move to work...otherwise it will result in accidental EX moves all the time and frustrating loss of meter. On the other hand, releasing block for that brief instant could also mean eating an attack... so overall, IMO, the execution of the EX moves is not well thought out.
Breakers. I'm on the fence here... I hated them in MKDC because many(if not all) of them launched and resulted in stupid damage combos. I like that the MK9 breakers simply knock down. I think that, similarly to KI, the implementation of "unbreakable" combos would be good because it gives rise to depth of play for higher level players who are capable of not only saving meter for a breaker but also be knowlegable enough on the characters to recognize which combos are breakable.
Dash vs. Run ... Of course, as a UMK3 player, I want Run.. Run created so much versatility and depth that I can't go into fully right now. The run button was dynamic, it allowed rushdown, it allowed combo versatility and combo lengthening... it was done perfectly and it's removal is sorely missed. Dashing, so far as I've seen is implemented fairly well... but I think only actual gameplay will determine what level of depth it will add to the game. I am happy to see that specials seem to cancel the dash so moves like Scorpion's spear will cancel a B,B dash.
Corner pushback. So far, I pray that it just hasn't been implemented in the demo vids we have seen. One vid that's been posted shows Cage vs. Mileena and in a combo Cage pops up Mileena and combos in the corner with no pushback. This WILL lead to broken characters, 100%'s and infinites if it is not fixed immediately.
I am VERY concerned about this game. I like some of what I see and dislike alot of what I see. This doesn't mean, though, that I'm completely right or completely wrong. I'm just being honest about what I see and I hope that the positive qualities remain unchanged and that some/all of the negative qualities are addressed in the final build of the game. This game has the ability to be decent, though I'm currently believing that it may not necessarily be a good game... right now I stand more in the "casual fun, but not tournament worthy" group for MK9. I hope I'm wrong and I hope that the gameplay, come March, proves to be far different that the observations I've made here.
The gameplay doesn't look choppy or slow either, looks fluid and fast