I've used pinterest to optimize my site and the result was amazing my site was jumped from #234 to #9 in few weeks time.
The trick is we must got our website pinned and repinned by many people this is the hardest part. Most of pinterest users won't doing repin when they aren't like what we pinned.
I do simple thing to outsource it on fiverr and got my site pinned by more than 70 people, I don't know how can he did it just search by typing pinterest on fiverr and you will find it.
As I know currently pinterest is best for SEO for these reason:
1. Once our website pinned it has 3 backlinks counts
2. Google interest in social media signal so it will not tagged as links farm
3. Currently pinterest links are dofollow even the image
4. Also support anchor text, it's perfect for placing our keywords