Google+ made a good first impression. It was definitely better than some of the other alpha release social networking systems I have tried recently. Usability was very good. The were a few quirks (such as posts not sorting properly), but crashes or outrageous memory consumption were not evident.
The four initial circles (groups in plain English), Family, Friends, Acquaintances, and Following, offers enough control to differentiate contacts based on how well you know someone. It is easy to create new circles but I have not figured out if you can make a private circle yet.
The Hangout voice/video chat feature is very cool and surprised me by working out of the box on Debian sid. Hangout could easily replace Skype but that depends on convincing my family to switch, which would not be so easy. D&D geeks are going to love the group chat capabilities of Hangout although I cannot say how well that works, since I only tried a simple one-on-one chat. And the mind boggles at the more, er, promiscuous possibilities of Hangout. ^_^