I tried out the arcade dump that leaked. It runs a little slow on my computer, so I won't spend a ton of time with it, but I still played it for a little while anyway. The game seems pretty fast paced, and I was still able to do a few easy combos and juggles and such, so it was pretty fun. There are lots of characters to choose with a bunch of different color schemes (Yuri in Mitsuharu Misawa's colors is awesome), excellent graphics, lots of nice backgrounds, nice music, etc., so it seems pretty polished.
Definitely buying this day one. I hope the online is solid since I'd finally like to get decent at a KoF game...