Sorry Ginny... had to rush off to an appointment before I could answer your question. I'm going on memory from a few months ago... so IMO, grain of salt, etc etc.
steved5600 is correct in his assessment of heat. They do heat up a bit less quickly, and they're slower to shed heat. Nothing dramatic... just noticeably slower than wire, and a bit warmer vape. I'd recommend an atty with cooling fins (like a TOBH maybe) and a delrin insulator before the DT.
I got some of the first test samples... used them in an old Helios with 2mm German silica, threaded through the center... and an Origen V2, with organic cotton make-up pad strips inside and a "bed" underneath as well - both were dual coil at 0.3Ω net resistance.
They vaporize juice as fast as any wire coils I've made in the same resistance range... too fast for just a pull-through cotton wick, so you need to expose as much cotton surface to the coils as possible. The silica did a slightly better job of feeding the coils... and of course, didn't burn like cotton if you got lazy with your dripping habits. ;-)
In all cases, the flavor was good... in some instances, a bit "different" (not better or worse, just a change in the emphasis of flavor progression on the palette) with the same wick and Kanthal coils.
I kinda set the donuts aside for awhile now, but as I've been using rayon wick (
Cellucotton) for 6 weeks give or take - rayon has excellent capillary action compared to cotton or silica - I may break them out again (I forgot I had them to be honest). Nice thing... the damn things are pretty durable.
The investment is small, and if you're an experimenter like me, they're certainly worth considering - but they aren't a replacement for a well done Kanthal coil. Cheers...