I'm using the minimum allowed by my LG GH24NS90, which is 16x. Have tried with 24x as well...
I've got mixed results... some discs won't play, some will, some will but then won't after some time. My PS2 reads original games and audio CDs pretty well. It also plays the games as long as I burn in my mom's PC, which uses a Samsung recorder (can't remember which model).
Since it's not my PC and this suggests some kind of problem or incompatiblity with my GH24NS90, I started looking for a new drive and ended here. But maybe it's just some kind of incompatibility between the media and my drive.
Ps.: The discs pass verify