Been thinking a lot about how Google works out what quality sites are (as we all have). Also tying back to a lot of the other advice from people who have recovered from Panda and their strategies in doing so.
A lot of people claim improving your metrics (bounce rates , time on site, etc) are a big part in recovery. Of course, this leads to the usual accusations of Google using Analytics which I just don't buy in to. For one, bounce rates in Analytics are entirely subject to how you have Analytics set up, so these could be quite flattering even if your actual engagement isn't that good. And then there are plenty of sites who still don't have Analytics installed. It just doesn't make sense.
So my theory is that Google is in fact using personalized search to make judgements on quality.
1. New visitor arrives at your site for the first time. Your site is added to their Google search history. So far, no judgement has been made.
2. That same visitor does a search and Google bumps up your site a bit in the results. If the visitor looks at the results and clicks on one further down the list, ignoring yours. What can Google learn from that user-action? Apparently your site wasn't good enough to make the user want to go there a second time.
Multiply that scenario by lots of searchers and you have a pretty reliable way of judging user-satisfaction in my opinion.
Now you might say that the searcher just happened to land on one of your poor pages on an unrelated term and Google shouldn't have sent them there in the first place. To which Google might say - why have these poor pages in the first place? And that feeds into the whole idea that you need to ensure you don't have too many thin and low quality pages, because clearly that will not leave a long-lasting positive impression on the visitor.
It also means that some other fairly hard-to-measure things like design and ux actually do end up having an effect on search positions. Poor design = poor first impression = bad news in search.
So there you have it, a fairly simple way of measuring "quality" or more accurately, "user satisfaction".
Now if only I could think of a good way to test this theory :) I guess the only real option is to just knuckle down and bump up visitor satisfaction and see if it improves search results at the same time!