As every human being is, he is subjected to a wide range of emotions, and is probably more succeptable to these than the average person. Therefore, as Crazy for Ivan posted: he has his good moments, and he has his bad. I think that he has an emotional link between him and the piano, and if anything is out of balance (attitude of audience on arrival, piano brand/tuning/voice, suit etc etc) he can be subjected to a bad performance. I noticed in his Scriabin Etude Op.8 No.12 video that he looked kinda pissed off with the audience, especially how hurredly he left and the look he gave them before he started.
Henrah