This new update is going take a long time. MY sites have been bouncing all over the the place since October 1. Google is doing many things currently such as, implementing newer filters for spam, updating PR, ect…
Although your PR maybe rolled back this may be only temporary this would apply also to indexed pages getting the boot. I would expect this to last as Kwblue stated at least to the end of January, 2007.
Combined with the million of complaints and drop in revenues Google has no other option but to take some aggressive action. I have noticed my backlinks are slowly being cleaned from spam, over a thousand removed porn sites removed. Basically Google has had enough and will be taking the boot to spammers.
At the end Google will be a cleaner SE for a while anyway. As stated in a previous post some programs who utilize spam techniques stand a good chance of being removed.
greek39