mattwnz:timmmay: This thread is quite funny. You guys are going on about the small savings going from CFL to LED, ignoring the much much greater cost of lost heat through having incredibly inefficient downlights.
If you really want to save money get rid of the downlights, or replace them with sealed units you can insulate over.
My downlights are insulated over, as they had special heat cans that allow this. But I acknowledge that many people have had cheap or older recessed lights installed that can't have insulation near or over them. Pendant lights are really the best in my opinion, when it comes to getting the most light, and no heat loss though the ceiling.
The main advantage for me with LEDs, is lifespan, as I will be installing them in very high ceilings, where it is difficult to keep replacing the bulbs. Halogens don't last long, CFLs, havea better life, but LEDs should be the best.
In my research heat cans weren't something that were a good option, only if the light was designed for them. My CFL downlights (which are gone now) produced little heat but I still couldn't use heat cans.