Light Emitting Diodes. Have you seen those new flashlights that are smaller and have a really bright light? Those are LEDs. Oh - outdoor Christmas lights that are often blue and purple are LED strings. These lights last forever (relatively speaking) and are very energy efficient. They're being used more and more for households.

LED (light emitting diode) lights are expensive bulb shaped clusters of many diodes meant to replace incandescent bulbs.

An even more interesting question is WHY are there LED lights:
It all started as so many things do today with the gullible and the sly. The problem was that all the patents on radiant light bulbs and the processes by which they are made had expired so anyone could get into making them but only a big third world facility stood a chance of making any money. Of course the answer to that was ban them as energy wasters and allow "efficient" CFLs (which contain poisonous mercury) as an interim stage while awaiting the mass production of the lab miracle, the "Photonic" bulb, a super efficient, very expensive, well protected by patents, cold light emitter. Needless to say, there have been quite a few potholes on this road to riches and mass production of "Photonic" bulbs seems far away. So the falling prices of LED lights allows another player into the game.

What are we going to do when all we can buy are LEDs? The LED lights give my husband massive headaches. I've heard others talk about this too. What about people with epilepsy? I think choice is a wonderful thing when it comes to lights. While I like the look & brightness of the LED lights & the thought of less energy consumption, others may not be able to physically handle the light they emit.

Here is a link that might be useful: Interesting Synopsis & Question on LED Lights By Lighting Engineer

I just wonder when incandescents are illegal, and they decide mercury is poisoning us with improper disposals, (Dead fish in our waterways, amphibious life gone, insanity, you know, little stuff like that,) if they're going to offer us "incentives" to replace our light sockets with ones that actually work with LEDs?

I have a 11 motion sensors and 12 dimmers, which can't use CFLs or LEDs. Where some LEDs have worked in dimmers, they burn out very quickly. Where I've used them in motion sensors, they flicker. I know, they're not supposed to, but I proved my electrician wrong when we stood in the bathroom in the odd, blue, flickering light.

So to afford the fixtures to promote their longevity? They gonna help?

Just a point of clarification - incandescent bulbs have not been banned.

The law that passed in 2007 set standards to make lightbulbs more efficient, specifically 27% more efficient through 2014.

Here is a link that might be useful: Lightbulb Q&A

If you're asking vis-a-vis deciding on something for your own space, like undercounter lighting, I think it's wise to try out a version of each of the options first. There are xenon, halogen, fluorescent (CFL), etc, in addition to the old standby incandescent.

I too am not fond of LEDs because of the intense greenish brightness they can have; I went for xenon bulbs in my undercounter lighting and have been satisfied with them - not as much loss of the warm "golden" look I cherish, which I find hard to duplicate with fluorescent, but more efficient than incandescent. (Although apparently not as efficient as some other newer options; the xenons do get somewhat warm.)

In CA half your kitchen wattage has to come from high efficacy lighting (i.e. flourescent or LED). I put LED cans and undercab in and love them. There is no greenishness at all. I bought "warm" color (2700). The xmas tree white LED lights i bought did have that greenish/cool tone that I didn't like.

I love my kitchen lights. They are warm and bright and really lovely light.

Under the EISA lighting requirements (in effect now for lamps with light output equivalent to an old 100 W lamp and phasing in for lower wattage lamps over the next two years), you have a choice of high-efficiency incandescent (including halogens), CFLs, LEDs, tube fluorescents, xenon lamps, and HID lamps (ceramic metal halides are supposed to have excellent color rendering, but like all HID lamps they have a restrike time and therefore aren't usually used in residential applications. But you could).

Some LEDs are hard to live with, but some are just like incandescent-- you have to do your research. We thought we didn't like LEDs and then we looked into it. Ours are also 2700 and we love the light they give.

Energy waste is a real concern. Not just an excuse for people who want to sell new kinds of lightbulbs.

"Where some LEDs have worked in dimmers, they burn out very quickly."

That would indicate thw power supply to reduce the 120 VAC to low voltage DC for the LEDs was not designed correctly.

These are usually switching power supplies, and while it is not all that hard to design one to operate from a dimmer, it can be hard to design one that produces decent dimming performance especially in a very small retrofit type packaging.

"Where I've used them in motion sensors, they flicker. I know, they're not supposed to, but I proved my electrician wrong when we stood in the bathroom in the odd, blue, flickering light."

Who told you they are "not supposed to"?

Most motion sensors use the same device as a typical incandescent dimmer, called a triac.
Triacs distort the voltage and current flowing through them, even when they are 'fully on' and providing no dimming.
This has no significant effect on incandescent lights, but on anything using a ballast, transformer, or power supply it causes problems unless the device is designed top tolerate the distortion.
On/off operation is easier to design for than actual dimming, but still needs to be accounted for.

'Magnetic' dimmers use a slightly different technology that alters the distortion so it is more compatible with transformers, but can still cause problems for 'electronic transformers' (actually just power supplies almost all the time) and ballast operated devices.

'Dimmable ballasts' often requires an extra wire from the dimmer control to the ballast, and the dimmer and ballast are a matched set.

The dimming is also not anything like incandescent light dimming.
The dimming may be anything from a few tens of percent to around 70%, but nothing as 'nice' as incandescent lights.

Dimmable CFLs have many of the same range problems.

This has been incredibly informative and helpful. Thank to everyone!!!

We have CREE CR6 LED's in all of our cans and we couldn't be happier. They are indistingushable from regular incandescent bulbs, have a soft white color, dim very well and are instant on with no delay like CFLs. To top it off they were reasonably priced at $25 with the trim (which would have added another $10-15 per can).

As more and more bulbs come to market the prices will decline just like they did with CFLs.