One. And you're looking at it.
Looks like it's time for another good old fashioned Sagara Science Experiment. The article makes some fantastic claims:
Compact fluorescents emit the same light as classic incandescents but use 75% or 80% less electricity. […]
Swirl bulbs don't just work, they pay for themselves. They use so little power compared with old reliable bulbs, a $3 swirl pays for itself in lower electric bills in about five months. Screw one in, turn it on, and it's not just lighting your living room, it's dropping quarters in your pocket. The advantages pile up in a way to almost make one giddy. Compact fluorescents, even in heavy use, last 5, 7, 10 years. Years. Install one on your 30th birthday; it may be around to help illuminate your 40th. [Emphasis mine]
I don't particularly care too much about the money savings — although that would be a nice benefit — but the convenience of having to replace a lightbulb only every 5 or so years is totally worth it to me. So, I'll give it a shot. I've heard that the CFLs still have a small delay after the switch is flipped on compared to their incandescent brethren, but I'm willing to give it a shot. If the delay isn't unbearable, I think we may have found ourselves a new type of lightbulb.