Nope

IMHO --Only "focus" on technique when you are practicing and there are actually exercises that have you use nothing but up strokes :eek: .

"Live" playing--anything goes--Violin bows (page), powered screw driver (EVH), the awesome sounds you get by lighting your guitar on fire (hendrix).

An upstroke has a different "attack" sound and could be usd instead of a down stroke if you like that particular sound or "fits" what you are playing or you just do cause you like it :p