i'm doing the whole john petrucci thing where i go up by 8 every time.

during these school holidays i've gone from the 180's to bordering on 200, not there yet but almost...

but i reckon anything over 150-160 bpm would be pretty fast, and 150 is probably the hardest to improvise with straight 16ths on. playing faster makes you hink less or something, i dunno, but my teacher always has me playing at 150 only using my thumb to push the pick, then only the wrist, then only the arm, and when your using the arm its definately easier to play at 180 than 150.

but i'm rambling now...i don't think i've said anything relevent except the over 150 bpm thing, so thats my answer...150 +