If you're referring to this type - yes, we've had them in two houses.

I think the first one was a Jenn-Air (I know the cooktop was a Jenn-Air) and the next one was a KitchenAid (the cooktop was a KitchenAid).

We never had any problems with either one and because of the design/appearance of both kitchens an overhead wouldn't have been possible.

I've never been one to turn on a cooking fan and as such, I didn't use the downdraft vents very often. The first one was built into an island with seating on the other side and the second was built into a peninsula with seating on the other side as well as being very open and very close to (or part of) a vaulted great room. I always had some concern about whether or not the up/down function would fail but neither one ever did and they're required by code (two different states) so it was an expensive necessity versus an option.

Re: heat shielding - I used to cook with people sitting on the other side of the island and don't recall any problems but in retrospect, I may have used it more often if people were sitting there because of steam or heat - but both areas were fairly large in width.

New models are much better than my 17.5 year old pop-up, plus a few rise higher - as much as 14" above the counter - but they still aren't as good at removing smoke, steam, and such as an island hood. Also, pop-up downdrafts are often noisier because they have more bends in the venting (more bends, more air noise).

I'm not against cook tops in islands or peninsulas or pop-up downdrafts but I think you may be testing the limits of a pop-up downdraft by pairing it with an indoor grill. A cook top with griddle? Sure. A cook top with an indoor grill? I'd recommend an island hood or moving the whole unit to the perimeter. Sorry, that may not be what you want to hear but better to know beforehand than to install the units and only use the grill once or twice before deciding that it just isn't a good fit (that was my folks' experience with a Jenn-Air cook top with grill in an island in a previous home).

You should post in the appliance forum to get information and recommendations about island hoods for indoor grills. There are some very knowledgeable folks over there. Fine Homebuilding's Kitchens & Baths Annual Issue (on stands now) has an informative article about powerful hoods and make-up air on pg 12 that may be useful to you, too.

Good thoughts. Our KD just came for an onsite walk-through and we decided the Jenn-Air just wasn't worth all the extra accommodations... especially the huge amount of cabinet space required underneath.

So, I think we'll probably stick with a heavy-duty overhead vent and gas cooktop with electric grill module.

Next stop: the appliance forum!

Thanks.