I most certainly do. I also thermostatically control the temperature to what I want. Some seeds I find require a specific temp to germinate well or at all. This year I had radish seeds some on heat, some off. The ones on germinated in one day at 28C the ones at 16C took a week. I also put a dome over them to keep humidity up.

SCG

I have one and sometimes use it to germinate warmth-loving plants like tomatoes, peppers, and vines like melons and squash. Apart for something like watermelons it isn't absolutely necessary but it sure does speed up germination. It does need to be monitored though so that things don't dry out too fast.

My basement has infloor heating and is a cozy place for starting seeds that require an extra bit of warmth.

I've used one for years. I find it really speeds up the germination process. Don't use it for seeds that don't want heat though. I only keep the containers on the mat until I see germination, then they get put directly under the lights.

Since my grow room is at 16C I like using them to get the desired optimum temp for some species. An example is petunias which like 25C as an optimum temp. With soil temps at exactly 25C I get faster and higher germination, I was skeptical and tested it. While some species it doesn't really matter some, IMHO, really do better at certain, if not just warmer, temps.

Do da! lol

Nope! My shelves have lights suspended from chains and anything that needs heat I grow in a dome with the light dropped right down to dome level. If it needs extra heat, I hike up the light underneath to give some bottom heat. The ballast end is the warmest, so that can be employed. I can easily maintain 25 degrees or more like this. The occasional seeds that don't want light I will just wrap the whole dome in black plastic and do the same otherwise.