Here's the way I see it.
First, the PR calculation gets fubar sometimes, so you'll see sites with a PR6 and have no idea why. Eventually it all gets sorted out though.
Second, when you see a PR6, that's just a graphical representation of PR6.42376539763 or maybe a 5.8425965824 or something like that. I don't know how they round the numbers off, but they do. Two sites that are showing PR6 don't really have the same page rank.
Third PR (as seen in the toolbar) is only one of many factors that determines where your page places (how your page "ranks") for a given search. I think this may be what Linkster was getting at.
Just my theory
