Pros : I LOVE THESE!!! I cut the 12" tiles into 4 piece to use in my kiln. They are perfect as I can still get my hands in when setting the tile down in the kiln. This allows me to set the tile in while keeping it perfectly flat. Nothing falls off, and I don't have to re-adjust anything before I close the lid! I have used them again and again and again. I have used thin-fire sheets on them for the most part, but find that after several firings there is enough of the powder left from the sheets that I can actually do several firings without anything. You go get a rougher back on the glass, but I don't care as most of my pieces I bead around so the back is covered any way. I have had the glass grab the tiles from time to time, so I would still recommend the thin fire. Using kiln shelves with kiln wash, etc. is just not my thing. I don't like having to re-coat the tiles again, and again. Also, I take my glass out when it is still pretty hot so these are great!
Cons : They are kind of messy...but that is the only negative I have. Of course, you can't use kiln wash with them as they can't get wet. But I prefer thin fire sheets any way.
Other Thoughts : Wish they made these for high fire ceramics...say to 2300 degrees or at least Cone 6.