Product review (5 stars): Why doesn't this come standard?
I'm surprised that this is doesn't come standard with all InSinkErator disposals.  A must-have in our kitchen.  I've read complaints about the stopper closing on its own.  Although this happens occasionally due to running the disposal and generally banging around in the sink, it has not been an inconvenience at all.  It keeps large items like silverware from falling into the disposal opening while allowing water to flow freely.  I do find it's necessary to remove the stopper in order to push food scraps into the disposal unless they're really small.