Unlike some others, what concerns me most is the network management issue in social-networks.
There is no pavements for standards (as we say). I'm not sure how thats going to help in giving the users a more 'Personalized' experience.
As I see it, there are pros and cons to each network on the web.
Facebook, as I see it is more likely a way for 'Casual' management of social contacts, you know, where things like 'be friends with' and 'Poking' happens. Though the same concept could not be followed, lets say if I want to have a social connection with my colleague and / or persons with whom I'm doing business with. People might have
different perceptions, but that solely my opinion. On the same knot, if I'd like to be a part of developments or progress of a company, doesn't mean I 'LIKE' it. Well, thats kind of no-brainer. Same goes with Twitter, for me its a great micro-blogging tool (which it is). But this is just what it is. Its not a social-network in a broad sense.
Most of the people are so excited about G+, as it offers a better and selective way of getting in contact of your friends (The adage of 'Circles'). The most important thing with G+ is that it will be highly interoperable with already existing Google services (Unlike adding a 3rd party-service like Skype, which FB did). Well, Google created a Win Win situation here. Google+, for me proves to be a tool that is focused more on communication and maintaining social contacts than any other social-network.