I just got back from test driving the e90 (325i step, and 330i stick), and we tried my MP3 CD that I always have in my X3. The intent was to see how the standard and premium sound systems compare.

What we did notice was some very buggy behavior in playing back my MP3 CD. Sometimes I would get a "CD Error" message and the disc would eject. Sometimes it would play, but when forwarding to another song, it wouldn't play a track. It would skip numbers, or sometimes multiple numbers would take you to different parts of the same song, or sometimes the player would just hang and give up.

As far as sound quality, I was quite impressed with the standard sound system. Lots of bass, and just good sound. The premium sound was certainly better, but I don't think it is really worth the cash. I didn't really notice a distinct surround sound effect. My wife used to be in band, and she was able to detect the surround effect. Another note - hitting "m" and then the forward or back button takes you up or back ten songs. It doesn't move through folders as with my X3. I'll need to test a CD without folders to see if my disc configuration confused the player.

I also have a vid of some of the erratic radio behavior (mostly skipping numbers - i.e. I go to 21, and it just skips over to 22).