For a few of my older sites (2 years+) these seem to have settled down in that they show the same spot in Google.com all the time and when I check on that one caffeine datacenter IP as well. For some of my newer sites the jumping around continues all the time. I guess that is slight good sign that hopefully things will begin to settle down once and for all.
I can also say this is the case, an older site is settled the new site lost 90% of traffic. However webmaster tools shows the new site is continuing to grow with more pages being listed, however searches dont yet reflect this.
Tomorrow/thursday is going to be a very telling day, the past 3 months we have seen search engine traffic increase considerably on th 5/6th of the month.
[edited by: Andylew at 9:12 am (utc) on May 4, 2010]