fastest i've got on -R (and indeed +R) for the 108 is just under 6x. my computer's pretty slow though.
it'll read burnt DVDs faster than it reads pressed discs for some reason.
bear in mind though, that this drive is a bit finicky with -R's burnt with other drives. i bought a spindle of crap discs (VDSPMSAB 01), and the quality difference between the pioneer and the lite-on 812S is amazing and disturbing.
i still can't make it read back most of the discs burnt with the 812S, which is a pity because i don't have that burner anymore.
it doesn't appear to have this issue with +R or even +RW media.