Its all good playing fast stuff but the majority of speed is only in soloing. When it comes to playing complex riffs and rythm, with the exception of petrucci, there is nothing much out there to give you a full workout when you are playing. So, I recommend Michael Romeo and his band symphony X. Technically and musically, Romeo exceeds Yngwies playing but I guess the only reason for romeo being how great he is now is cause of yngwie but the standards are a lot higher now. So for solo's, you cant go anywhere but petrucci. And for rythm, try out symphony X with Michael Romeo. The fastest solo I have ever seen was Tony Macalpine when I met him at a Planet X concert. Believe it or not, what you hear on a CD is actually 85% of the artists full speed potential. I saw some sheredding that would make you give in the guitar ( I nearly did).