Our home was built in 1990 with a Jenn-Air grill, downdraft and coil units.  The downdraft works well, but is very noisy.  I like to cook on the grill, but my husband doesnt like the smell of the grease from grilling inside.  I replaced two of the burner units, and none of them seem to work very well. I cannot cook with more than one burner at a time.  Not sure if it is the fact they are plug-in components, or it is just tired.  I will replace it when we remodel the kitchen with a smooth-top  down draft.  I like the downdraft in the unit rather than a separate pop-up downdraft, which are very expensive up to $700-900.