I have six slabs that are replacement tops pieces for the Fireview, or slightly bigger. I keep at least two of them stacked on one side of my PH if I am not cooking. They do indeed get very warm...about 50 degrees cooler than the slab under each, so if I have two slabs and the stove top is 400, the slabs would be about 350 and 300. I use them for cooking: this variation in temperature gives me lots of choices for various foods. They add mass and retain and radiate heat as well. And every night they are used as bedwarmers, and radiate heat all night. Wrapped in a beach towel they make the beds toasty and are still warm the following morning. I have twice used them on the hood of my car to start the engine when it is below 30 below out and very windy. I have used them to melt ice that was keeping a door closed. They really are effective as storers and radiators of heat. On days that suddenly drop and are bitterly cold, if we have been outside and feel chilled when we come in, we'll wrap a slab in a towel and put it under our feet, mohair blanket over the legs, and it's very pleasant to sit thus in front of the fire and chat, read, watch a movie, whatever.
The same weight of soapstone will retain twice the BTUs as iron, and radiate them more slowly.