Have you ever used one of those new LED light bulbs?

I picked up a couple, mostly for under counter lighting, and they seem to be pretty energy efficient, as they burn like 10,000 hours, use one-tenth the energy as incandescent bulbs, and produce very little heat.

Some others I have gotten are outdoor yard lights that have a solar cell on top of them. I am going to use those as spotlights for my Halloween display.

Have you used them? Do you like them? Would you replace all the lighting in your house with them if the manufacturers could get them to be big enough to provide all the illumination that you need?