The CFL bulbs in common and regular use are those with a standard E26 (Edison screw) base.

I have a number of CFL recessed fixtures in my family room which were installed a few months ago. They don't get very high usage, but I'm planning on installing the same fixtures in my kitchen around the counter edges, 4 in total. They're 4" recessed fixtures using GU-24 pin bases with 18w bulbs. $20 retail gets you the fixture including bulb, which is a lot more expensive than GU-10 halogens where you can buy a six-pack for $36. I can get a better price, but they're still on the high side IMO. That's about the most I'm willing to spend at the moment though.

These lights are not popular at all. I only know of one local chain that carries them and I have never heard of anyone else installing them. My brother installs lighting as part of his business and has never had anyone request them. Usually customers simply go for GU-10 MR16 halogens when doing recessed. They're by far the most common and have been for a long time.