I'll add to the confusion by adding that jitter reporting of my Benq units, with the same discs, have had variations of +/- 1.5% depending on firmwares, models (1640 / 1650), and units (two 1640s with same f/w didn't report the same jittter levels). No, I'm not referring to burns with different units/firmwares, but to scans of the same discs.
My 2 cents: unless one can see an obvious increase in PIE in the same place as the jitter increase, and jitter levels stay under, say, 13%, one shouldn't worry.
Just like PIE/PIF reporting with some drives (like the NECs), this jitter reporting feature of the BEnqs is far more useful to compare burns than to check the "absolute" quality. If it was possible to judge the quality from jitter by scanning in Benqs, the manufacturers wouldn't have to use the extremely expensive CATS equipment...