Agreed. PR is essentially about link popularity, and the original formula has been tweaked over the years. It now probably include factors like the quality and page position of the link, not just a raw link count.
When you're comparing PageRank values, always keep in mind that the scale is not linear. The difference between a PR 3 and 4 is a LOT less than the jump from PR 4 to 5... and that kind of difference goes all the way up the scale.