It will make an impact. I have had authorship set up for months now and it has made a difference to click-throughs.  Basically I have more traffic now than before.  And I believe this is partly due to the photo in the SERPs.

We put an authorship plugin together for WordPress as we needed to implement authorship on our own sites and client sites.  It's free - you can try it if you feel you can't or don't want to do it manually.  http://www.authorsure.com.

I realise this response is almost a year old, but I've only just found it. I am about to start using Optimizely, but am concerned about affecting my ranking especially now that we have a new Penguin update due any time now.

The nice guy at Optimizely told me today (during the webinar for newbies) that you could use Optimizely to permanently direct different sorts of visitors to different content. For example, he pointed out that people who today run IE 6 are very different from people who run IE 9. And depending on your market it might make sense to give those two groups different messaging.  But Google specifically say don't deliver different content based on user-agent.

http://googlewebmastercentral.blogspot.co.uk/2012/08/website-testing-google-search.html  And on the last point in that article, how long is too long?

I took  "simply falling down in the SERPs" to mean that it's preferable to an actual penalty. We are all rising or falling in the SERPs for every keyword every day according to what changes happen in and around our sites and in and around other people's sites.

Google is trying to use a bunch of signals to imply authority and quality and along the way they are bound to judge some well intentioned sites wrongly.   Someone I know has a site full of original and useful content. But he also has a whole bunch of duplicate content pages lying around which he forgot about from months ago, and a long list of duplicated archive pages due to poor use of tags in WordPress.  He's placed a large ad above the fold on every page and has a high code to content ratio on the page. He has poor but not non-existent social interaction on his site and his site as a home-made feel to it - it also looks dis-organised - which I tend to think prevents people from ever engaging with his stuff as they can't see the article for all the surrounding clutter.  He uses GA so G knows about his bounce rate too.   You can't fault him on his content, but in the past when he didn't know better he did some fake link building but he doesn't do it any more.

He lost 75% of his traffic on 24th April.   At least if this a result of  "simply falling down in the SERPs", he can simply climb back up with a  few changes. Except for the bad links.

I'm not sure what anyone can do about those, but then I am (reliably) told Penguin had nothing to do with inbound links.

Liz