alan speed control comes in handy in a few instances.
if a drive is particularly loud when playing back a movie slowing it down can reduce noise and make it less annoying.
if you're having a hard time ripping, some say that lowering the read speed is helpful, but I'm not sure if there's anything to back that up...can't hurt though.
if you right click the options you get the following explanations:
Default: the default speed of your drive
Slow & Quiet: use this while watching a movie
Medium: Compromise between speed and noise
Fast and Noisy: for when you need data fast e.g. while copying
anydvd doesn't have much in the way of a help file, but its right click functions better than any program ever. if you right click ANYTHING it will give you a brief but detailed explanation.