I've fallen in love with the character design. Backgrounds are beautifully detailed, though a little bright and can detract from the characters. The system is very, very cool as well. The Critical Counter System is one of my favorites as well. I get a little excited when I get to pull it off.

Besides the lack of stages, missing of one or two modes and not-so-great online play, I don't think there is much wrong with King Of Fighters XII. I know that in itself seems like a lot, but I hope they learn from this experience and just add to this game for XIII.

I like it a lot, too.  I find the gameplay, art direction, and graphical execution great.  As it is, the "game" itself is perfectly fine and a nice break from SFIV IMO.
The only problem is that the lack of modes has left me a bit wanting.  It isn't so bad right now as I'm trying to learn the ins and outs of characters, but soon I'm going to want to play against live opponents and that doesn't seem possible right now.
Other than that, I would go as far as saying that I LOVE KOF XII.  I just wish there was a little bit more to love.  If it were a value-priced game, it'd be perfect.  It's just kinda hard to recommend at a 60 dollar price point.

I love the systems in this game. The Critical Counter system is amazing. I firmly believe that this is a great game for parties, as well. This is one of the few games you can probably play with a girlfriend.