By the look of it, Google is currently running its latest PageRank Update. Seosydneyblog.com has moved from a PageRank of 0 to a PageRank of 4 and a couple of websites I manage have also seen their PageRank increase this morning.
As noticed in the past, the update usually takes a couple of days to settle, so do not get too ecstatic because the PageRank scores might still change.
Regarding the rankings, I have not notice many big differences as the rankings'changes usually take place over a larger period of time before and after the effective PageRank change.
The last Google PageRank Update took place mid- January, just after one in October 2007. Based on the last three consecutive updates, I would suspect that Google actually proceed with the update every 3 to 4 months, which would bring the next one around July-August 2008.