Compact fluorescent bulbs

These bulbs use only 1/4 of the energy of incandescent bulbs, cutting costs and reducing energy demand. The New York Times had an article about Compact Fluorescent Lights (CFLs) on the weekend. It was about how some people don't like them because they don't always last as long as expected, they don't dim, the colour is different, and they have mercury in them.
There are three reasons for poor longevity: cost cutting in manufacturing, and inappropriate uses. To try to get costs down, some manufacturers have reduced the quality such that the bulbs will fail within a few hours. CFLs don't work well in places where they are turned on for short periods (like closets). Another cause of early failure is placing them in enclosed spaces where they can overheat. Tight spaces and rapid on-off cycling are inappropriate uses for these bulbs.
The other complaints are being addressed: dimming bulbs are available, the amount of mercury is being reduced (and stores like Home Depot will recycle your bulbs), and different colours are available.
LED lights are also susceptible to damage from heat (incandescent bulbs are tolerant of high temperatures
The Times has a Topics round-up of stories about CFLs, including this
Video about CFLs.