If it's below 25C, I'm *cold*. Also, I'm not a huge fan of frostbite. Soaked mittens or gloves are a good way to get it, even in a "heat wave" of 0C. So it's a YMMV thing.

I haven't experimented yet, but they're also supposedly helpful as a layer in very low temperatures. Think below -20 or -30C. Use them over or under a regular pair of gloves to get more insulation where it counts. (course, if it's *that* cold, I'll probably be cowering inside with my teapot )

Problem is, most biking gloves aren't designed to insulate. So I don't know how helpful the fingerless versions would be for this sort of thing.