I have it, and it's pretty decent.
the main problem with it, and with most iphone games, is that the controls are a bit iffy but SNK came up with some clever ideas on how to get around it. For instance in order to get a neomax you just tap your characters face, supers you can just tap the super bar, there's a button that triggers HD, etc.
it is also interesting how the game is pretty damn similar to the console release, with trial modes, tutorials, and a bunch of the console exclusive stages.
if you want a surprisingly decent port of KOF XIII it'll do the job, but it's not like your going to actually be able to practice the game on the go.