Last year around this time I tried a dimmable R-40 floodlight that didn’t really work. On the advice of a commenter on that post, I ordered some Greenlite R40 23W dimmable floods and they are a very good replacement for our incandescent R40 floodlights. They dim smoothly and reliably, and unlike other bulbs we tried, they fit, and the dim down almost all the way — the box says there’s a little integrated circuit in the bulb. The box says the 23 watt bulb uses 70% less energy than a comparable 75 watt incandescent, and that the bulb lasts 6 times longer than a standard bulb. The color of the light is pleasing, even when dimmed, which is one of the major complaints I have with other dimmable CF bulbs.
I got mine from 1000bulbs.com. although there are several inaccuracies in their specs: this bulb is a 75W output, not 100W as stated, and in one place they say the color is 2700K (very warm white) and in another 3200K (warm white). On the bright side, I replaced 100W bulbs with 23W bulbs, and while we have less light, we’re using 77% less electricity (actually, I guess that’s both the bright side and the dim side :-)