With the pre-school/baby market I think they work well if they already have a well known name. Otherwise you may as well start your own group. Buying a franchise was something I was considering a few years ago.
One acquaintance of mine was badly burnt when clients were paying the franchise direct, who than ran off with the money. it was a recruitment franchise, so she had workers who were waiting to be paid, and companies who had paid....nightmare mess.
I don't have a franchise but I live in a fairly rural area and am aware of some people locally who have committed to a franchise that works really well in busy areas but if you don't have enough people in your area then it will fail. Or more specifically people with money. I'm talking about the baby/preschool activity market but I'm sure it would be true of any franchise. Do your research and although the 'package' may be very appealing will it work in your area and if it will why has no one snapped it up already?