I put one in the opener for a while, but switched back to the incandescent. Even the 100w equivalent CFL was just too dim when the garage is cold. My garage opens onto a fairly dark alleyway, so I wanted more light so my wife wouldn't hit anything important
I did, however, put CFLs throughout the rest of the garage (100w equivalent "daylight" units)...and they're great! I don't need them to come on instantly...and they only take a minute or so to get to full brightness in the cold.
This pic was before an el cheapo garage makeover (fresh paint, homemade cabinets, etc.). Maybe I'll post some pics sometime to show how much difference can be made on a small budget in a small garage.....