That depends on the discs you use, some support faster burnings than the others.
Some software can test the optimal speed to use with each one.
I understand that some people defends that speed is not important any more, but if time is not your problem keep speed to the lower side, as some video editors do when they produce a DVD.
Also, I've a CD writer - a Yamaha 1FE - that has a feature called Audio Master Quality. If you select this one the drive doesn't allow you to burn faster than 8x.
Considering that it can do as fast as 44x, it can meam something.
By the way the reduced speed was explained as due to the AMQ techs, and Plextor just started selling a CD-RW with this feature (Premium 2).