Now that the beta is public, should all those questions made in Google+, that are suitable for SE, be actively redirected here?
If the question has been sufficiently answered here, definitely yes.
If not link the person to StackExchange, recommending it as the best place to get questions answered, or to Launchpad, as the best place to report bugs and feature requests.
As not everyone is happy to register for yet another site I'd still offer assistance there, I would consider anything else to be rude. In case the person asking for support does not do it himself, port the question and answer to SE (if it adheres to our rules).
(I believe this applies not only to Google+, but also Reddit and IRC.)
I'd certainly advise this.
It is much easier to track questions (and answers) and it gives a central place to point users when they run into issues. Take Ask Ubuntu for example. Search for almost any common (and uncommon issue) on Google and it's probably been posted there already, and if not answered, at least you know there is somewhere to find an answer without the dead back-and-forthness of a forum.
Google+ is a great place for users to show off their desktop and interact with other members of the community, but a terrible place for real support with technical issues. To make matters worse, you now have to log in to view public posts on Google+ (an announced change, recently implemented on the network).