The work you have to do to put it together.  It says you shouldn't use a drill to put it together (it invalidates your warrenty etc) but seriously there is no way you could get the screws into the wood without one, especially when putting together the sides, it's at a weird angle that you just couldn't do by hand *and* get the screw to connect into the wood.  Even then in using a drill, it has to be a little one so that you can get the angle.  Then you also drill the screws into a deep hole, also incredibly difficult to do without a drill.  I've got it constructed it, but not without losing the will to live.