Why are we still continually putting "panda" and "penalty" into the same sentence? Hasn't it been made abundantly clear by now that affected sites don't meet Google's new criteria for quality. As a consequence, those sites now have changed rankings.... some slightly different than pre-Panda and others a lot different.
Google rolled out Panda because they believe it can better detect quality signals. If we continue to focus on trying to find and fix "things that got me penalized" we are going to remain stuck in SEO 2000 mode.