tedster - 7:20 pm on Sep 16, 2012 (gmt 0)

withing days/couple of weeks, your rankings came back. That suggests that if I make a change and my rankings don't come back within a couple of weeks, I still haven't addressed the real problem Google has with my site. But is this still true post Panda and Penguin?

If you have a Panda or Penguin problem, then your rankings will only recover when there is a Panda/Penguin update or data refresh. Those two named sub-algorithms are sort of isolated modules in the total algorithm.

Other than that, if your ranking problem is something else then, yes - you can see recoveries in a short period of time at almost any time.