Hi Mapman:
Some of the technical stuff would be compression, etc. But, what I hear a lot of the time from cds sounds mechanical, like it is not quite human. Sometimes it is very bright sounding and uncomfortable. I guess the main thing I notice is that I get listener fatigue pretty quickly with cds but not with analog.
It is not the case with all cds. Steely Dan's Gaucho sounds great on cd, but the analog copy of Aja is much better than the cd version. The cd version of Van Morrison Astral Weeks and Moondance sounds awful compared to the analog versions.
I have been buying analog lately that includes a cd copy along with it, and that allows me to make really direct comparisons. Rilo Kiley "Under the Blacklight" sounds great on analog, bright with no bass on cd.
I'm not sure if it is just my ears, or what. But, Analog seems more involving and less tiring. I've tried to factor out the whole ritual of playing analog that might effect how I hear it, and I think I have been able to do it.