I've read that you don't want your peppers to set fruit until the temps stay above 60 or 65 degrees. Temps lower than that supposedly lower yields. Last year we transplanted them out with small fruits on the plants, and the yield was pretty poor.
Last year's transplants:
I think having fruits already set kind of slowed them down, because they had to adjust to being outdoors while working on growing peppers. I hope that this way they'll have a short time to acclimate to the weather and new soil before blossoming.
We're still having really cool nights here (40 degrees a couple days ago) so I'm reluctant to plant them out without any protection at night.