My initial impressions.
First-off, DAMAGE CONTROL-- The game is supposed to be getting a PATCH ADDRESSING THE ONLINE PROBLEMS BY THE 28TH. Let's give them a chance before outright bashing them; BlazBlue's netcode was not at its stellar level until it too got patched. (Although still far better than this game has been)
For some time now, I've felt that KOF XII seemed like a beta. The game comes off as unfinished in several areas-- some characters don't animate as well as others, move sets for some characters feel limited, there's a lack of game modes, an end boss, and only six stages to fight on, with two of them being palette swaps. The game doesn't even have character taunts!
The lack of clarification on the game's netcode also had me worried, and unfortunately, while KOF XII's netcode is better than SNK's Xbox Live Arcade fighting game releases, it still pales in comparison to the competition. Hopefully the forthcoming patch will fix all of this.
Playing KOF XII offline and online feels like two different fighters. Offline, the game is fast and furious, with incredibly responsive control and an great character animation. The game plays smoother than any KOF before it, and the added critical counters, which thus far do not feel like they break the game in any way, plus changed-up CD attacks give the game a type of "focus attack" and "parry" system. The way that characters' attacks can also cancel each other out also gives the game a fresh feeling. It's cool to see a physical attack cancel out a projectile, for example.
XII's visuals are a mixed bag. The backgrounds look fantastic, and there's some trademark SNK humor going on in them; it comes off like a Metal Slug game on steroids, and while the character sprites are HUGE and very detailed, they are also incredibly pixellated, and filtering them only makes them appear too blurry. Comparing both versions of the game, I find that the PS3 version actually looks a little better than the 360 version does. The game's animation is very well done, but I don't know if it tops the now decade-old Third Strike; some characters definitely look more animated than others. While all of the sprites go well together, Athena looks a little bizarre, as her head (and eyes) are massive in size compared to all of the other characters.
I want to reserve judgement on this game until the patch is released. Right now I am very impressed with the game play overall, but it needs to have good netcode to make it a complete package. If the patch does fix the game's current (horrible) problems, I'd recommend KOF XII despite all its shortcomings, but if not, stick with Street Fighter IV and/or BlazBlue, and wait for the next (finished) iteration of the game. Here's hoping!