I have a few Caran d'Ache colored pencils and they're great! Their pigment is very strong, so the color comes out really vivid. Too bad mine aren't watercolor pencils. I can't say much more or compare it with other brands because I don't work with traditional media too often, but they're good quality for sure.
Never heard of them before now. The only thing that really sound that alluring about them is that they're water insoluble, so you can use them with watercolor. They didn't seem to have a clearer or more vibrant finish on their own than Prismas did from what I saw. Can't imagine they're worth the huge price hike over the already expensive Prismas, unless you really need them for that specific application.
I hadn't heard of them either before the other day and neither had my art teacher. I'll have to try mixing them with watercolors when I get my samples to see how well that works. If I don't love them in comparison to my prismas though there's no way I'm buying a set.