I overclocked my 40125W some months ago and have been very happy with the result. I noticed a considerable improvement with VS08 with some faster burn speeds and only a rare yellow block in CDSpeed.
Using real time burning, not simulated, I found the following differences with the media I have at hand.
Disk brand, Possible Manufacturer, Claimed speed, Real speed VS08, Real speed VS06
TDK Gold CMC, Imation All speed 48x 48x
TDK Blue Ritek All speed 46x 32x
Sony LeadData 32x 31x 31x
Datastream Prodisc 40x 47x 40x
Kodak Kodak 16x 31x 31x
Taiyo Yuden Taiyo Yuden 24x 39x 39x
Taiyo Yuden Taiyo Yuden 32x 39x 39x
Imation CMC, Imation 24x 48x NA
Laser Postech, Diamond 40x 31x 31x
Unbranded Acer media NA 48x NA
Mitsui Gold Mitsui 12x 40x NA
BASF Emtec Kingpro 32x 46x 24x
Philips Ritek All speed 47x 39x
TDK Ritek 12x 24x NA
Using the unbranded cd above, including lead in and out, it takes 2:52 minutes to burn a SVCD from a 763Mb bin file. Hopefully these results will help others.