Happen to bump into this Google Panda update info graphic which gives a good quick overview of what this update is all about. And yes, this update is a real website traffic killer and it won't care whether your site is an authoritative site or not as long as your web site contain negative points that shows up in the Google Panda algorithm, you will be whacked!
So far I have tried to clean up whatever I can, but I have not seen any re-bounce to the website traffic that I had earlier. Perhaps my site still contained a lot of negative points which are deemed less useful and thus not worthy of inclusion into the better ranking on the search term.
On the other hand some sites owners seemed to have good inkling as to what Google wants and has managed to take steps to rectify their site and get better results. But with so many tweaking done by Google, chances are it is a long uphill climb to the former higher traffic for most of us hit hard by changes. I guess there are many points to fixing the Google Panda update penalty.