I use them both at my school (7-12) and at the Coder Dojo I mentor at (mostly kids years 4-7-ish) and they are an absolute hit.
I've been having a blast looking at different concepts and projects which I can use when teaching Digital Technologies (the Australian learning area for CompSci types of ideas).
Personally as a teacher they've also done a world of good for me in learning about the basics of electronics and getting a better understanding of embedded programming (had some fun optimising MicroPython code to do what I want).