LEDs are replacing incandescent and even CFL bulbs where power is expensive (from batteries or solar panels). They can be powered by either AC or DC and, while expensive, can be the perfect solution for the right high-efficiency lighting need.
Here is a good product overview:
http://www.theledlight.com/catalog.html
Below is an article that tests light output from the three options. (This by the gear heads at Solar Washington).
http://solarwashington.org/newsletters/0503/LEDsROCK.A02.pdf
And just for fun.... Here is another article from the same newletter issue on a simple solar panel setup that provides 12 DC power for such lights (and the computer and the radio...)
http://solarwashington.org/newsletters/0503/corbin&iris.A01.pdf
Considering I want to try replacing my light bulbs on LED lights. What are the pros and cons?