I suspect that you might not be impressed with one compact bulb (or even a couple). Compact fluorescent bulbs don't put out nearly as much UV power as a traditional blacklight, so they have to be pretty close to the target. I used one last year in the yard, and it was OK, but I only used it because I could weatherproof it easily.
For my FCG, I use 2 24" standard blacklights, and I think that I'd have needed 4 compact bulbs to equal the same amount of light. By the time you bought 3-4 compacts and the clamp-type fixtures to hold them, you could easily buy 1 or 2 traditional blacklights.
That said, if you have a place in which a traditional blacklight fixture won't work, the compacts in a clamp fixture may be the way to go.
HTH!