We get on great, so that side of things I'm not worried about. Its the space/practicality/safety aspects, really. I'm pretty sure we'll have to go for a wide beam, which would 'help' with most space issues (Not sure how much help, but if we moved to land, I'm not sure how much bigger a space we could get anyway), but I'm still not sure about practicality/safety stuff.
We're on the Thames (as in on the river not in a marina, but we're on the marina wall, so hookup, permanent mooring, etc.) so space for the boat isn't an issue.
Apart from one or two big cruises, most of our cruises are day/weekend trips, but we're prepared to stay put for a while.
I know a couple of families that have moved onto boats when the kids we're a bit older, but I haven't met anyone with a newborn/first child yet.