2006 CFL sales for the US were announced. About 95 million were sold. This is a little bit less than one per household, there being 105 million households.
So it is time to abandon the "If everyone were to buy just one .... " advertisements in favor of "Now that we are saving .... " advertisements. This will be an interesting transition. The early adopters and holier than thou eco-fanatics don't like it when the unwashed masses accept a technology. It becomes so plebian and ordinary. But CFLs are making that change. With current models offering a variety of color balances, shapes now being reasonable, and prices becoming quite low, the CFL sales are transitioning to the basic mass market approaches. 2007 will easily exceed 2006. I think price changes were the primary factor. The price is now low enough that you recover the cost within a year. This means that renters and leaseholds now consider CFLs to be a reasonable purchase. (I doubt that this is a conscious careful accounting analysis, but renters do hesitate to spend money on things that will be left behind when they move.)
The next CFL challenge will be dimmers. I saw my first successful CFL dimmer installation a few weeks ago. It didn't have nasty flicker and did have a reasonable range of dimming. It did not require an exotic dimmer control either. The CFLs were not as cheap. They cost about $15. This is still a money saving choice, but nowhere near as attractive as non-dimmable CFLs.
After that is the challenge of the candelabra bulbs (those little ovoid things), track lighting, and reflector bulbs. These have both more difficult shape and size issues, plus usually need dimmers.