Now I use the Nec 3540A and 4550A to burn CDs. Both give most excellent audio CDs up to @32X - fairly steady jitter levels around 7.5% with good (RITEK) and superior (MCC, TY, MXL) CDR media. Even CMC discs turn out great in these drives at high speeds, jitter always stays under 9% in all cases.
Actually you elaborated on my implicite point: this depends on the burner. For example my Benq 1640A induces too high jitter (in my book) on audio CDs at anything but 12X and 16X… slower and faster writing speeds are less good. Jitter may get as high as 32% in the worst cases. :Z
As a sidepoint, with 48X and 52X rated CDRs, I noticed that slow writing speeds (under 12X) always give less good results jitter-wise (still in MY drives ;)).