bumping this again bc i ran across this in the bmw press release introducing the m3.as many have said,it's leather. this answers it definitively for me:
Four exclusive trim strips extending throughout the entire width of the dashboard beneath the Control Display and instrument cluster, provide further options in customising the new BMW M3. The “basic” trim comes in Titanium Shadow, with Aluminium Shadow and special leather tanned in carbon design as well as high-class wood in fine-grain surface design and platane wood in Anthracite all being available as an option. In each case, the trim strip gives the interior of the new BMW M3 its own very special touch ranging from cool
high-tech to sporting elegance.
here's the link to the whole press release-
http://www.m3post.com/forums/showthread.php?t=55136