For no apparent reason, my index page and domain/key-term.htm page have swapped positions (my index page is now on page 2 for key term, and the /key-term page is now on page 46).
There haven't been any significant changes to either page since the index page fell from page 5 to page 47 on 1 December.
I noticed, as I trawled down to page 46, that several of the sites that had incomprehensively risen to page 1 in May have fallen 20+ pages now.
Whatever Google's intention, the outcome of Panda and Penguin - with nonsensical and impermanent penalties and rewards - has been instability that has lasted over six months.
Presumably Google's share price reflects the fact that this is driving more and more of us to adwords, and driving more and more frustrated searchers to click on them.