I have to add - in the light of recovery for some - that our traffic has recovered slightly. I am down now 10% compared to the average of 2 weeks prior 24th of Feb. BUT: My improvements on the site has increased the conversion rate by 20% compared to the same time frame. So, I am back on track because of Panda, which triggered improvements on my site.
The whole user behavior aspect of Panda is the most promising theory so far. There are also some simple improvements you can do along the list we gathered here and they helped for me.
Maybe the conversion rate improvement will impact the ranking or not - yet I feel much better :-)