Last year it was plowed but still closed to cars on May 22-24 when this crazy guy did it, with some great pictures: http://www.crazyguyonabike.com/doc/OhMcKenzie
PS - This other crazy guy did McKenzie Pass at the same time from the east side: http://www.crazyguyonabike.com/doc/McKenzie2012
. He got a picture of the rider in that first link and also another rider up there. Sheesh...crowded!