It’s been pretty commonly agreed for quite a while that PageRank (in the form that’s publically viewable) is a number that just doesn’t match up to the real authority of a particular site. The latest post from the Webmaster Tools blog solidifies that fact that this just isn’t something to base your success metrics on.
The key phrase of the article?
…PageRank comes in a number. Relevance doesn’t.
Anybody with any marked SEM experience would agree that conversions are the ultimate goal. Beyond the obvious (conversion rates, bounce rate, number of conversions), there are a few numerical metrics that I like to keep tabs on.