I have the same experience: my site was a mess, i had like 6 million pages in google, and about 4 million were all duplicate pages. My site was loading 3 times slower than now etc etc...
After i first got hit (in October) i worked hard to correct everything. Now i zero duplicates, zero errors in WMT, etc.
And yet a lot of messy sites with millions of duplicates are rising and shining on first page. At some keywords, i even see two duplicate pages from these sites on first page.
And my site hasn't recovered, only lost rankings in April and now in June again resulting in a total 60% loss.
I'm wondering if ANYONE knows a real definite example of panda recovery, cause i doubt it.