When it launched, many people in the Portland web design community wrote off Google+ as another product soon to end up in Google's graveyard, like Google Wave, Buzz, Gears, Knol, and in a few months, Google Reader, but in just under 2 years, as of January 2013, Google+ has surpassed Twitter to become the second largest social networking site in the world (with Facebook in the #1 slot). Aside from the social features like hangouts, messaging, games, etc., the biggest benefit of Google+ can be to your SEO. Here's why:
#1 Google's priorities have changed
My search for "web design" on google might be different from your search for "web design" because Google considers your personal search history and the activity of people in your social networks when generating a page of search results.
Another notable change is that Google doesn't care about meta keywords anymore, but they're factoring in your URL, page title, heading tags, whether your code is validated and uses the correct semantics, proper grammar and spelling, and even the author of your posts. And it's not surprising, but they seem to give preference to Google+ posts over other social media platforms.
Google+ gives more weight to posts that are written by authors who have a track record of regularly posting popular content that gets a lot of +1's or shares across other social networks. The more popular an author, the more likely the post is to show up in a relevant search.
#3 Use hashtags to stay organized
The system of hashtags used by Google+ is very similar to what's used on Twitter and Facebook now. By handpicking your hashtags, you can make sure your posts are categorized properly, which could help your placement in search results.
#4 Extend the life of your content
Instead of posting simultaneously to your site and Google+, stagger the posts by a couple of days. This will keep traffic coming to your site at a steadier pace, instead of in spikes. A steadier stream of traffic is not only good for your site's performance, but it's great for long-term organic SEO. Google+ will know that your content is coming from your site, so you don't have to worry about cross promotion being seen as duplicate content. That being said, don't double up on everything your post. Your site is a separate entity and should be treated as such. Use your best judgement.
#5 Circles for targeting your audience
Circles allow you to split up your audience into groups based on interests. This is a great opportunity to create specific content for a few different segments of your audience. Let's say you have Circles for Online Marketing, Local SEO, and Portland Web Designers - you don't have to bug your online marketing circle with a post about local SEO. You'll maximize activity around your posts and minimize the loss of followers.
#6 Google+ as a blogging platform
Unlike Twitter or Facebook, there's no character limit, so feel free to post longer content to Google+. Google gives some priority to Google+ posts, so a Google+ post about Portland web design would be more likely to show up higher than a tweet from a Portland web designer. A preview of content is your blog is ok, but don't copy all your content. Unique content is always better.