of course the belt drive thing is CEC marketing. They make very good transports, but to suggest that they are inherently superior because of their drive mode is taking things a little bit in the direction of the marketing department. As you suggest belt drives introduce problems of their own that are not inherent to direct drives.
+1
A friend had the CEC TL2N (Which I believe utilizes 2 belts?) for a number of years. He purchased a P.S.Audio Memory PWT and in his audio system both sounded very well. They provided different sonic presentations and some listeners preferred one over the other (No surprises with that).
Point is they were highly competitive and the PWT is not belt driven. So as is often the case, there are multiple ways of "skinning the cat". Belt drive and direct drive mechanisms if executed at a high level can be very viable options. I do agree that attention paid to limiting vibration is critical for improving the sound quality of CD transports. There are numerous ways to achieve this as well.
This is one key aspect (Among others) that seperates the higher quality and better built/engineered transports from cheaper made units.