If you've got the means to wire up the fluorescents, then by all means, your plants will love you for it.

I just recently started adding CFLs to the floor of my growroom. I was just using a 600W MH/HPS, and wanted to get some extra light to the undersides of the branches. I made several independent fixtures using desk lamps with adjustable necks. I took the original 100W bulbs out of the lamp and fitted the socket with three socket extenders each. Four 23W CFLs go into the sockets, and away you go. They're very efficient in that you are able to bend the lamp in the direction that needs light the most. I'm using four of these lamps at the moment, along with a new 1000W system that I just got. Can't wait to see how it turns out.

Since I use a switchable MH/HPS system, I decided to go with cool bulbs to supplement the MH, and warm bulbs for the HPS. The plants seemed to fill out a bit better in veg and flower using this method, but I'm still experimenting with it and can't confidently speak of its effectiveness. It definitely doesn't harm the plants...I can attest to that with confidence.