Thanks for your replies. Here are my thoughts -
Googleplus is used more by techies
Facebook is more fluffy and geared towards stalking ex-girlfiends
Twitter is for chatterboxes
With that said, G+ is Google - meaning that they want to promote G+. Coupled with the fact that GAuthor allows for credibility from authors it should be a no brainer that GAuthor has SEO value.
The more GOOD posts you write, with comments (which must help) and likes etc, then the more Google must surely place on your credibility within your niche and rank your well written linked content.
I work in tech (information security) and we all use Google Plus - in fact - I have an almost zero FB exposure (but I do get some traffic from FB).
What I am saying is simple stuff but surely G+ and GAuthor are joined at the hip - not least because of the <rel=> meta tag......
Im kinda new to G+ and GAuthor so let me know if I am talking sense or just plain BS
There's also a growing belief that Google is going to start using something called "Author Rank" (or maybe it's referred to as AuthorRank).
My hunch is that you are 100000% correct with this Author Rank principle. Is that your term or is that Google's official term - Author Rank?