Besides their somewhat steep up-front price, LED bulbs (lamps) aren’t without a few other drawbacks. Some new models are dimmable, although they don’t dim to low light levels compared to halogens and incandescents. In general, avoid discount LED brands and shop for long warranties and Energy Star ratings.
Most down-light manufacturers now offer a dedicated LED down-light, which is really a system that includes a housing, an LED “light engine,” and a “driver,” which regulates current. Many of the residential airtight insulation-contact IC rated LED down-lights are lensed to reduce glare. It is good to examine the options in person to see which products offer the best glare control and light quality. LED lensed down-lights are typically available in 4-, 5-, and 6-inch apertures, and would be used for general illumination such as in a kitchen, bath, laundry room, or hallway.
For more controlled and dramatic effects, there are adjustable LED down-lights, which perform in a similar way to a halogen MR16 accent light, including lenses to control beam pattern. A 20 W dedicated LED module produces the same lumens (equivalent of a 50 W MR16 halogen lamp) with 50,000 hours of life—and it’s dimmable. The color-rendering and beam control are quite good with the higher-end products.
There are also some great LED track-lighting heads on the market. They can be expensive, but the beam control, punch, and color rendering are all good. Reputable manufacturers will have photometric data and performance specifications verified by independent testing labs. Avoid manufacturers that cannot provide this material for evaluation.
Another lighting technology entering the market is called electron-simulated luminescence (ESL), and is based on cathode rays, like old TV sets and computer monitors. The bulbs (about $20) currently have limited distribution, but they produce warm, yellow light like standard incandescents. They are roughly as efficient as CFs and are said to last as long, yet they contain no mercury.