Cleaning disks any good?

Hi m8s

A friend has a Sony combo drive (DVD/CDRW) that has suddenly started to be picky with some disks that it read well in the past (burned DVDs and DVDRWs). Should I recommend him to buy one of these cleaning disks that they sell in the TV/video store?

What is the best type of cleaning disk (if they are any good)? I think they sell some with some kind of fluid and some that have a brush on them and don’t use any fluid. There are CDs and DVDs.

I was wondering if they do any good to DVD writers like the Liteon LDW811s, and what about stand alone players like the KISS DP-500?

Thanks guys.