All i know is that there is a direct correlation between the wind conditions and having the reefing line rigged. Every time we don't rig it, we wished we would have. It is very difficult to rig when you're caught in a squal trying to keep off the lee shore, the boat upright, and people on the boat. Ask UDecide from the Trans Tahoe several years back.
Like Mike said though, it makes for a much more relaxing commute back to the dock after a long day of being over powered and light on crew. We have set it on one race that I can remember. It wasn't fast, but was a lot more enjoyable.