I just took delivery on an '04 S55. Since I'm a gadget geek, I was very interested in the MP3 playback capabilities of the new COMAND system on 2004 CL and S class vehicles (especially since there's no glovebox Aux jack). Anyways, I found that the front slot can not only read MP3 CD-Rs, but MP3 DVDRs as well. I posted my testing results in a related MP3 playback thread on the E forum. Here's a link to that thread:

https://mbworld.org/forums/sh...mp;pagenumber=3

Since it's not an officially documented feature, nor do I suspect they officially support MP3 playback off of DVD-Rs, some features don't work as well as they do with MP3 CD-Rs. See the thread for more details.