Irresponsible. Gutsy, if it was only the M3 on the road but, IMO this driver put several lives in danger. Best I can tell is the AP managed as well as it did by the contrast between the black pavement and the white snow edge. Yet is still failed several times. Also, I've seen many cars [right in front of me] drift into the slush at the edges and get thrown into a nasty spin-out. No thanks. I'll probably use AP only on interstates, and only in clear road conditions.
Don't forget it is currently Level 2 driver assistant, I think it did really great considering conditions. No other Level 2 system can come close, OK I have not tried Mercedes, but I guess they are on the VW level.
But I agree it was dangerous thing to do.