I had 2 sites hit with Penguin. 1 has 100% recovered. It's actually higher for certaon secondary phrases than it was before I was hit.
The other got hit by Penguin AND the "gaming links" email (they aren't the same thing) That is still recovering and now has about 80% of the traffic it had back in April. It's making more cash though as I improved my conversion rates.
For a couple of months I was really pi$$ed off, but the recovery was sure enough.
No 301's - No massive link blasts, just added content constantly and linked sensibly to the new content. The "link gamed" site had BMR and another service links on it, so I contacted the admins of those schemes and got them deleted. About 6 weeks after I did that the site began recovering properly (went from outside 500 for a phrase it was once number 2 for, back into the top 50, and has been climbing ever since)
4-6 months for the first site
Almost 8 months and counting for the second
Moved on - made more sites, but as an exercise in seeing what Google "likes" it was quite useful. (if f%^king expensive for a while)
Scritty