I assume they will keep the SERPS frozen for a while just to evaluate the impact of the changes ( user behavior, etc )
They're definitely not
keeping the serps frozen, for the record. I've just had a new site jump 5 pages this morning for one of its main keyphrases. (To the sweet and heady heights of Page 15. Damn it baby I'm good. Megabucks, here I come!) If anything, I'm seeing SERPS to be more fluid than normal. I put that down to more and more data being read by the new algo and the serps shifting as a result.
A bit of general advice - Don't assume, and don't trust what you read here or elsewhere. Ever. Anyone decent and making a lot of money in this game will keep their best tricks close to their chest. Its business. A lot of other people will have the best will in the world, but not know what on earth they're talking about. I've had plenty of wrong ideas about SEO when I started out. Some of my stuff may still be wrong. Test. Think the serps are frozen? Track a few keyphrases and find out. If you assume the serps are frozen, you are limiting your scope to experiment. In the meantime, someone like me will test, will figure things out, will use it and will beat you in the rankings. I know that makes me sound arrogent - but I really do usually win, and I do it by taking everything I read with a pinch of salt and testing different ideas on junk sites. Just some advice.
Anyway. On-Topic. I suspect my client base is different to some of yours (No adverts, no thin sites, usually quite specific niches, often brouchure websites), but to me the only effect I've seen is on sites who have articles on generic article websites as part of their backlink profile. I haven't touched this form of link building in years (Too much effort for too little result for my tastes) and my more recent projects seem completely unaffected by Farmer. Some of the sites I used to place articles on were on that 'biggest loser' list thats been floating around since the update.
Those clients who have seen a drop tend to be consistent with part of their backlink profile being discounted rather than a penelty as such. I wonder, if those of you experiementing with onsite changes, have considered that farmer may of hurt the sites linking to you, as opposed to you personally, and what you are seeing is the knock-on effect?
Anyway. That's my data set. Hope it helps :)