This comment by Matt Cutts on PR gave me a clearer view on it:
Matt Cutts Said,
June 3, 2008 @ 9:31 pm
“…But remember that we only push PageRanks to the toolbar every 3-4 months”
If it was that important a metric surely they would be aggressively updating it – if not for webmasters then at least so that Google users will be able to ascertain at a glance if a site is an authority or not.
Is it worth keeping an eye on? Sure.
Worth losing sleep over? No.