Having just done the 2 Day M School, I definitely love how the coupe handles. I used to do a ton of track days on my motorcycle (NOW THAT is a rush). My fear with taking the M is the cost of repairs should something happen. I know from motorcycle track days that sh*t happens and when it does, it doesn't matter who's at fault. Everyone is on their own for repairs. Replacing parts, body panels, etc. on a motorcycle is relatively cheap. On the M...not so much.
The weight def. does concern me. The other thing for me is that I just don't get out on the motorcycle as much and on days when it's nice, a convertible def. bring a different but fun pleasure of driving. I drive the car hard when I can, but I also know the street is not a place for stupid driving. I'm getting involved more with my local BMWCCA chapter and they have an HPDE day coming later in the year so who knows. I guess I want the best of both worlds, but I'm not sure I want the compromise. We have awful first world problems on this forum...