After getting back into the SERPS for main key term and edging slowly back up the pages, whatever happened in this latest round has dropped my site another 12 pages. Some of the competitors I track have also shifted substantially (most of them downwards, but a couple have gained).
Obviously one can comment about the merit or otherwise of sites that are doing well or badly, but this constant and long-term instability is like having Google play Russian Roulette with our livelihoods.
It seems to me that the only people who can benefit are exactly those - the quick-buck spammers and black-hatters - that Google claims these measures are intended to weed out. Nobody who is in it for the long-term can afford to watch their site behaving like a yo-yo for the length of time this has now gone on.