I'd say Panda is one step in the great "sea change" that impacts all online navigation - and it's only going to get more intense. This sea change is fueled by the touch interface in all its forms (smartphones, tablets) as well as speech recognition.
All that spells the evolution and eventual death of "ten blue links". Touch and speech, not typing. And people using a touch or speech interface cannot afford to spend time investigating low quality websites.
Don't look to Bing/Yahoo for anything different. In recent interviews their spokesmen are putting forth a vision of the future that sounds more like Google than Google does! And a recent study reported here showed that on average, a search on Google results in an organic click 51% of the time, whereas a search on Bing only results in an organic click 27% of the time. I expect both numbers to go down.
And then there's Apple - have you checked out Siri? The whole online environment is changing. And Panda is one step toward learning how to meet the new online environment.
With recent Google changes, we did lose something from our lives that we really cared about - and this brings about something like grief response. It seems to me that many reactions to Panda are in the denial stage of "grief" and others are in the anger stage. But neither of those stages allow for effective adaptation. We saw a similar thing with the Florida update.
We're not going to reverse engineer all the Panda factors - and even if we did, new factors are always possible at any iteration. One thing I do like to watch closely is branded (even navigational) search traffic versus unbranded. And a second factor is direct traffic versus search traffic. When branded search traffic and direct traffic are healthy, then Panda usually seems to be appeased and generic, unbranded search traffic also cooks along.
Panda seems to take aim at sites whose business model was gaining generic search terms alone. That makes sense, given Google's stated motives. After all, this was the quintessential traffic profile for content farms.