I too am keen to hear from anyone who's seen recovery or significant drops
One of the larger EU automotive parts distributors, had previously seen massive drops in rankings - pictured below, showing number of top 5, top 10, top 20 keyword rankings (SEMRush.com data).
Their homepage had been virtually erased from the index, with many inner pages being down in the page 10+ range, up until this last Panda update.
The update has seen their homepage restored to mid-page 1 for hundreds of terms that it hasn't had decent rankings on since 2012. Virtually every page on the site has enjoyed the benefits of this homepage strengthening. While it's nowhere near the former glory of the July 2012 levels, it represents 100% gains over where it was a few days ago and is a faster rate of gain than the rate of decline seen (if you were playing the chart backwards in time from right to left).
What's been done to make this happen?
Massive quantities of footer links on every page - gone
Site skin looking like a refugee from back when Kirk commanded the Enterprise - gone
Oodles of static html doorway pages - gone
Tiny text, tiny images, keyword stuffed internal links - gone
Cookie cutter manufacturer information used as mainstay of pages - gone
The site is still being rolled from old to new, with too many manual steps to be believed, but core has seen crap either discarded, 301'd or rewritten, embracing a modern design, juicy photos and text written to be easily consumed.
There's more content writing going on than you can shake a stick at, with 2 different teams competing against one another, in terms of quality, cost, timescales and most of all, rankings gains. The new URL's associated with their content are the ones appearing out of nowhere within the top 10 to 15 positions, as some of the old pages jump upward, and some of the old pages not moving much at all.
While this has been one of the few that I've seen shooting upward after Panda 4.0, it is an example of how a site can start to recovery, given sufficient momentum and modernisation.
This is early days and there are thousands upon thousands of search queries, but overall, the path appears to have been validated as a sound one. Rewriting poor content, rolling up multiple low value pages into lesser quantities of high value pages, improving the user experience via design and user interface changes and social syndication. A straightforward recipe.
Note:
You did not see me mentioning a ton of backlinks being built, because there haven't been.
Quality content has been produced and published on site, consuming the old/bad content, rolling it up into more engaging, more valuable pages. The only backlinks have been those via social media syndication and some occasional earned link opportunities which were initiated by other sites, but they are few and far between.
This isn't a low budget project, but having doubled impressions and clicks, it's now net

ositive - with cash flowing in from the results much faster than flowing out (to pay the marketing teams).