i don't think people buy speedplays because for their lightness, there are lighter pedals out there (think aerolites). speedplays have several advantages over other pedals.

adjustable float - important for those with knee problems and those, like me, who don't want knee problems

dual sided - no more looking down or kicking the pedal trying to find the cleat. just step on it and go.

colors - for those who's bike is eye-candy

low platform height - for those who like to pedal around corners

cleat to shoe contact - larger than shimano and look

in my experience those who criticize them have never tried them and those who try them don't ride anything else.

but enough of that, back to wheels.