I would love more impressions of 4-player multi. I have no idea what "the Wii U starts to wheeze a little" means or what "stable" means. It's locked at 30fps, right? Do the visuals take a significant hit? And what is it like in comparison to MK Wii's 4-player mode? The same? Improved?
I have been known not to be eagle eyed when it comes to framerate, but I can tell the difference between 60 and 30 easily, 3/4 player drops to 30 yes, but I never noticed any drop, afaik they're stable 30 fps.