There are some pretty awesome videos of him playing things like Beethoven's opus 106 piano sonata (one of the most difficult piano compositions around. Certainly the most difficult that Beethoven wrote) and Rachmaninoff's 2nd piano concerto.
Kastle is an as because in all his comments he praises himself, but says things in such a way as to imply that he isn't himself. That is to say he refers to himself in the third person with a screen name that doesn't make it clear that it's himself that he's talking about.
That was almost clear.
Anyone who can play the piano impresses me, so this guy leaves me nearly speechless. Yes, this is as close to speechless as I get.