Although my site has not yet recovered from Panda, a friend's site has and there may be something to be learned by comparing the two sites and our different approaches to Panda.
His site contained his own content except for one section using affiliate feeds, and he had a technical issue causing duplicate content (thousands of pages). In April he removed the affiliate content and fixed the technical issue, then left it (continued operating it like normal but didn't keep changing things). He recovered with the September Panda update.
My site is small by comparison but contained very little content of our own. I made major changes (added huge swathes of our own content, combined similar pages, restructured the site, dealt with technical issues) and continued to change things for months. Traffic got worse and worse until we stopped changing things at the beginning of October and left it to settle. Rankings and traffic began improving about 6 weeks later with a significant improvement from the November Panda update (although it basically brought us back up to where we were when Panda hit).
We are actually now ranking better for some terms than before Panda but overall traffic is still around the 50% mark.
The conclusion I've drawn from this is you have to leave changes to settle for months before you'll see any signs that you may be on the right track. If what we're seeing is the beginnings of a Panda recovery then you may see minor signs of encouragement after 6-8 weeks (some terms may rise a position or two). I'm not getting my hopes up but we are seeing more and more encouraging signs every week.