If I make I brand new site: www.pagerank-importance.com I then approach a webmaster buddy who offers me a link on one of his related sites. One of the sites is PR3 and the other is PR7. Nobody can deny that the PR7 link will influence SERPs more than the PR3 link. So without a doubt, PageRank is important for search engine rankings It might not be the pagerank of the actual page but the pagerank of pages linking to it.
Page rank can really help your website especially when you are competing with other site, you can know your page rank by installing google PR toolbar.. or by using online tools...
From my experience PR does have an affect and here are the two biggest factors I've seen: 1. Age of site or domain - I have old sites with old content that still keep PR5 and PR6 and have revived expired domains and received good PR very quickly. 2. Use of Google API's - salarymap.com got PR5 after 3 months and while still under construction. I didn't see much value in the site other than it was a Google Maps mashup.
I think Bobby is correct. I don't think much has changed in the past 3 or 4 years anyway, other than increasing Google anti-spam measures. PR was never the major factor. It was always "one of more than 100 factors".