I find I miss the simplicity of Facebook to a degree. With plus, it's not really clear who I'm sharing what with at any given time, or what the relationships I've set up are. Facebook has one kind of relationship (1-1) and one kind of sharing (to your friends or to everybody, depending on how your security settings are configured).

It's also missing a number of essential (at least for college students) facebook features, like events and richer profiles.

I'm playing with it for now, but I don't think I can manage two social networks and since nearly all of my friends are on Facebook it's not hard to choose one. Maybe some day that will change, but network effects augur otherwise.

Edit: I should note that hangouts are seriously cool, and they might be reason enough for people to start using it.