Hi i am agree with all of you but i also added some formulas for calculating page ranks:
PR(A) = (1-d) + d(PR(t1)/C(t1) + ... + PR(tn)/C(tn))
a page's PageRank = 0.15 + 0.85 * (a "share" of the PageRank of every page that links to it)
Wow, that is some difficult math to compute right there. My head hurts just looking at that formula. Page rank is still valid, but the algorithms Google uses are so very complex that one formula is not going to explain it properly.
I believe page rank is still used to determine crawl priority and depth of a site. While still used, you still want to focus on the quality of your content and your links.