I'd have to agree with the "nitpickers." I somewhat play the piano (I was always better at Trombone than Piano, but playing the Trombone isn't really fun by yourself), and I can admire the skill with which he can play very fast and intricate fingering patterns - as that's my major weak point on the piano - extremely fast runs, my fingers just aren't dexterous enough (which is odd considering how fast I'm able to type).
In any case, I'm impressed with that, but his timing is, as mentioned, awful (pretty odd considering practically everyone knows how these songs are supposed to sound), and he also is just banging away at the piano for the most part. It could be the sound quality, but he doesn't have very good "play", "touch", or "feel" (whatever you want to call it) on the keys, and the's obviously never heard of a slur either (the pedals would help there, I don't think he's using them at all, and it could be put to good use at some points in there).