I think Eric is right when saying it's unfair to compare Google+ to the behemot that is Facebook. However, I'm not so sure that will ever be able to compete with it. The problem is not in the offering, I think Google+ has strong features and integration to numerous tools. But in this domain, the user base is all it counts.
I think the ace in the pocket of Google will be to be able to import a complete Facebook profile in Google+ : pictures, videos, contacts, posts, history, etc. Maybe then would people be willing to do the switch, providing contacts of them would do the same too.