Product review (1 stars): Very unhappy with this cooktop.
We have owned this cooktop for about 5 years and will be replacing it shortly.  The grates are not even, so pots need to be carefully balanced and can't always be centered over the heat source.  The grates are like a table with uneven legs.  The burners are very close together so it is difficult to use all 4 at once, or even 2 on the same side.  The downdraft is impossible to clean.  You have to reach down and fish the filter out, and grease collects in the well.  The downdraft fan is loud.
About a year ago we needed to have the unit serviced because the pilot was not igniting.  We learned that the knobs must have retained small amounts of moisture after being put in the dishwasher, which, over time collected and caused the unit to malfunction.  Service charge $275.

On a positive note, it is relatively easy to clean with the special glass cooktop cleaner.