LED lights are still not as efficient as fluorescent ones – but are better than incandescent lamps. They do, however, switch on very rapidly. You may have seen recent cars with brake lights that come on very quickly, much faster than ordinary bulbs which have to warm up. There are also LED traffic lights which can be seen to switch quickly. Their life is considerable, too, provided that the operating conditions are observed: typically 35,000 to 50,000 hours compared with 10,000 to 15,000 hours for fluorescent lamps and 1,000 to 2,000 for incandescent bulbs. I’m suspicious of the compact fluorescent lifespan: I’ve had to replace several on our outside lights, although these may be suffering from significant temperature variations.
LEDs are currently very expensive although the lifetime cost may be less than other light sources. In our kitchen we have downlighters set into the ceiling (which is low to match the rest of the house) I;ve replace some of these with compact fluorescent reflector bulbs which are fine when they are warmed up but do take 10 minutes or so to get to working condition: not very convenient when we want to pop into the kitchen to make a pot of tea! I’m looking out for LED replacements – but not at a price between £100 and £300!
If you want to read more about LEDs, I suggest you have a look at Wikipedia. And of course there’s a web site selling LED lamps - www.ledbulbs.co.uk
Incidentally, we still have incandescent lights on our tree – because they haven’t failed yet – but the lights on the porch gable are LEDs.