yes, I used a few LED’s for Baby Boots, my last short film. As we were shooting on the 7D with a nice fast lens, in a pitch black woods i found them absolutely indispensable, low power so they worked on battery which saved having to have a generator running while shooting, and because they were so small we could position them inside the car. The light from this is very cool (blue) but it was ideal for what we needed them for. I would also recommend using them during the day for close-ups, just to make the eyes pop, its adds a great glint in the eye but is weak enough not to affect the natural light surrounding the subject.
also used them for this little monologue piece… tiny room we shot it
check it out for led lighting