My ears don't seem to hear a difference, but some say record at a slow speed.
It would be doubtful that you would hear a difference unless there were audible errors (glitches/pops/clicks/etc) that were the result of burning at too high of a speed. I think generally, burning at 4x instead of 24x is not going to make the sound "clearer" or "better" somehow.
If your burner supports burning at 24x or 48x or whatever, I'm sure that it will do it just fine. The problem is that the burner isn't the only link in the chain. I think a bigger problem is that a lot of the newer high-speed blank CD-Rs are more prone to errors no matter what speed you burn them at. As MachineHead said, Pio2000 and several other people have posted on this topic over at HA Forums.
That being said, I burn discs for a friend to listen to in his car while he drives for work. If I burn them at 8x, he can play them but can't skip from track to track. If I burn them at 4x they work perfectly. The cd player in his car isn't more than 4 years old, but it's just finicky. In my car and also on my 15 year old hi-fi cd player the discs work fine no matter what speed I burn at.
Rob