Its a car for those who can afford two cars. Z4M for fun and trackdays and another car for everyday-use.
One member on m5board.com own a M5 and he recently added a another family member, a Z4M Coupe. So now he own both a M5 and a Z4M
Same colour as the one you drove?
http://www.m5board.com/vbulletin/showthread.php?t=80869