Sorry I've been a while - I decided to do you all the courtesy of getting the real numbers, and a holiday got in the way whilst I was doing that. Here is a graph for 5 different search terms which I follow, where the vertical axis is my position on Google for a UK search, and the horizontal axis is the date. The PR8 links were published on 26th January, I ran the chart for 3 days before & 12 days after.
Welshguy - no I have never bought links, and don't do link swaps either. The PR8 sites are the Washington Post & Techcrunch - do they have a reputation for selling links? I wouldn't know. The detrimental affect on my SERPS was pretty instantaneous do Google act that quickly?
Nikki - things have got slightly better, but haven't recovered. For my 5 keyword combinations my SERP positions:
The day before the links 48, 18, 19, 19, 11
Three days after the links 96, 14, 37, 37, 11
A month later 57, 24, 100+, 20, 10
None of this has made a significant difference to traffic from Google.