I don't have one but I wouldn't recommend it. I like my iolite by its self and with that I hear it will just heat up faster and it falls out and burns a hole in what it touches when you try to empty the chamber. Good Luck.
I have one, I like it and use it often. It distributes the heat a little more evenly through the bowl, and takes up some volume (uses less weed). Gotta be careful, like the above poster said, it gets hot as fuck. If I'm only going for a one bowl high, I use it. If its a two bowl high or group session, I use it in the second bowl. I also don't take it out of the house so I don't drop it somewhere.
i guess i wont worry about it for now. if only i could change the bowl size when adding that piece. i dont feel like im getting enough from 1 bowl. ive heard dont pack too much but ive tried just about everything. i usually need a whole bowl or 2 to feel it. each round lasts me about 10min