Product review (5 stars): The GE JP989 cooktop is great.
GE JP989SKSS ProfileTM 30" Downdraft Electric Cooktop is better than expected.  I was concerned about the 400 CFM downdraft, but it is strong enough to pull steam from sauce pans out of the kitchen.  I had a few questions about instillation for GE and this is where the rubber meets the road. GE Tech Support bent over backwards to answer all questions about instillation.  I installed it myself.  It took several hours. Removing the old cooktop also took several hours. The hardest part was connecting the downdraft vent to the vent pipe.  Simply use 6 inch flexible pipe and clamps which can be purchased at any home supply store.  I had to crimp the male end of the exhaust pipe to get the flexible pipe to easily connect.  (Crimpers can be purchased at any big box home supply store, or go to a sheet metal shop and they will probably do it for free or a nominal cost.  Specs call for a 40 AMP circuit breaker.  We had a 30 AMP for our older cooktop so we had an electrician come out to install a new 40 AMP breaker.  He convinced me not to do it.  He said, "if you start popping the breaker, then simply call me back to install a 40 AMP breaker, but the average customer is not going to have all burners on HIGH simultaneously".  He is right.  Might have one on high to boil water, you don't do normal cooking on the high settings. This is a great cooktop, far superior than our Kitchen Aid.  The major reason for deciding on GE was parts.  GE carries parts for ever.  When Kitchen Aid discontinues a model, they don't carry parts and we were forced to purchase the GE due to not having available parts from Kitchen Aid.