Legally, I think there is no difference--same rights and protections.
I think privately it's a bit silly (why not just do a registry office marriage?) but you know what, if it persuades even a few people to avail themselves of marriage-style legal protections before having kids/buying property etc. together, it can only be a good thing.
Unfortunately, the majority of people who have children while cohabiting and never get married, are probably very unlikely to do this as well, so it will probably help only a few people.
(Just to clarify: I am not bothered about people "having kids out of wedlock" for old fashioned religious type reasons; I do worry about spousesusually womenhaving children and putting their careers on the back burner without the legal protection of marriage/civil partnership. They can end up badly screwed if the guy dies or leaves them for someone else.)