Who cares if he tremolo picks the notes (Wich he does!) or how many or little frets he plays while doing it! Try doing the over and under (No I don't mean the piano technique..the other one he does) michael angelo speed.....Not impossible but you'll be spending a few extra years with this technique to get it up to Michael Angelo speed (wich I practice for about 30 mins. a day). Yes it's all for show and looks damned cool live. When Michael is in the studio..he plays normally.

Is he the fastest? No! He even says he does not care about being the fastest. The fastest I have ever seen is Francesco Fareri:
http://www.francescofareri.com/main.htm
Download some of his sample videos and be ready to be HUMBLED! IN A BIG WAY! :-)