It seems no one has commented on the Philips Xpanium.
It's a $200 player from Circuit City (perhaps elsewhere), but it's the first one that just WORKS. Of 500 mp3s that I've burned and played on it (RW CDs, 80Min CDRs, overburned CDRs), I've only had 1 or 2 mp3s that have had problems playing. Even CDs "coasters" from failed burns still play up to the point where the burn died.
It's expensive, but it works and pretty well at that. If you're serious about mp3 CD players, take a look at that.