I burned music onto a cheap CD-RW (you know, the stack of 100 for about 10 bucks from a PC warehouse)
After about 20min. it started severely skipping to the point where I got out of the car, removed the CD, and flung the CD about 75 yards (it was a pretty sweet toss) into a pile of rubble/dirt at a home construction site.
Next I tested a Staples CD-RW, this works much, much better. I notice skipping on a few minor road bumps after travelling for about 45-50 min. listening to the same CD-RW. 10-15 minutes later, it seemed to skip on almost every bump on the road (I think I sneezed once, and it skipped
Long story-short; for me, CD-RW are just fine if you listen to it once and then switch to a "real" audio CD.