Have a look in this paper (PDF format):
Jitter, what it is and how to measure it
A rule of thumb when scanning for jitter on a BenQ drive is that you want jitter to stay below 12% (not counting random spikes that result from the scanning speed "dipping" at certain points).
There is some discussion whether BenQ correctly reports jitter when scanning discs not burned in a BenQ drive, but no final conclusion has been reached on that subject.
There is a very experimental beta tool that makes it possible to scan for jitter on recent LiteOn drives with experimental firmware. See this thread if you're interested.
Plextor drives can also scan for jitter, but they don't report an absolute jitter percentage, so they can be hard to interpret.