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I'm doing it right now, and have had very positive results. Not necessarily in traffic, as I'm down 5% of traffic even after Panada's 50% cut, but the CTR shot through the roof.
I've just cut 50 000 pages away: low content, and duplicate content issues.
A combination of 301 for moved pages, and 410 for pages permanently gone, has worked wonders.
Google has taken many months to take it all in, and I guess it will take another couple. Nearing the end of it, overall traffic and page views per visit are all up.
It does require a manual intervention from their end to release a panda flagged site.
Why bother automating the process at all if you're just going to have to manually review every site it flags? I don't buy it.
If a bunch of sites come out positive at the end of a run, they would definitely want to make sure they have sufficiently changed to become positive.
It's also the fastest least effort way of moving forward.