Mo said: "A neglected website of mine with lots of (not so great) content rocketted onto top of second page from absolutely nowhere. Other sites with good link profiles seem to have dropped. "
I've seen the same thing. Two sites in the same niche - one main commerce site and one supporting information/community site. The latter has been largely neglected over the last 18 months. Few updates, no link building.
The former is constantly updated with good, substantial content, is supported by social media activity and has good new links built constantly. It is a strong brand in its niche. The info site, on the other hand, is not strongly branded.
The weak, neglected site is now outperforming the main commerce set for our trophy keywords and for several other volume, high conversion phrases. Some significant drops for the commerce site.
For us the change happened on the confirmed Panda 2.5 day at the end of the month.