In my podcast interview with +Jon Henshaw
he shared the need-to-know aspects of how SSL impacts SEO. I think if this topic had a relationship status on Facebook, it would be "it's complicated."
My main take away is hold off on SSL for now to avoid the hit in organic traffic and rankings. However it's probably going to be something to invest in for the future of the site. If you make the switch, take the time to do it right!
Listen to Jon's responses and decide for yourself if now is the time to make the switch. +Raven Tools
has some really useful tools and resources on this, too!