i watch it in fast play
unless its something that can only be played in quicktime... which in that case it can't be watched in fast without the sound skipping and overlapping (or maybe its just my sound card?)

but my style has been changing... i'd watch a bit, do what i saw, then repeat
i found it wasn't too productive, so i watch all the way once and go back if i forget something

although i found with ragecgi's layer tutorial there wasnt really any need for fast play