I have used them since they first came out - been like 8 or 9 yrs. I put them on all my spoon rests. They work great at between 1250 and 1275, which is where I normally cook them at. I only use them during my final firings, and have never tried them at the torch.
I didn't like the results using them at the temps that the directions recommend- probably has something to do with my kiln specifically. I don't have many full color ones left as they don't supply them much anymore but here's one of the 24k and white ones - although, now that I think of it, this might be one of the high fire ones - can't remember - I use them both the same way and at same temps - decided I didn't like altering my fire schedules so I stretched the temp of the directions to fit my schedules LOL