Is anyone really surprised Google is leveraging their search dominance in other areas that have previously failed them?
I stated from the first day I saw it.. G+ will be dominate, if not for any reason that for the fact that Google will continue to push it until it is.... oh and it hates it when people go to Facebook and Twitter first for fresh information.
This is why "freshness" is so important to the latest Google algo changes...
So what to do if SEO is your world? Start building circles like nobody's business. Getting +1's for your pages are great, but building power circles in your niches are perhaps even more important.
If you have say a "potato farming" website, I'd suggest have a large circle of farmers on G+ would be a very good start.. (and yes I realize that most likely their aren't that many farmers using G+ .. but expect that to change with the G+ integration into search.)