It seems like some of my sites have lost PR but gain in the SERPs and vice versa. Is PageRank still as important when it comes to rankings in the SERPs?

I think it still matters, but so do other factors such as anchor text etc. I use several tools to try to get a better feel for how well a site should rank. See smartpagerank.com for example.

Page Rank in Google depends on the amount of quality backlinks that you have.Where as SERP'S for any major Search Engine depends on the amount of traffic that your website receives for a keyword or keyphrase that you relate.On the whole SERP's are more important but in Google PR is important, the reason being it is because of the PR tool that Google has an added advantage over other major Search Engines.

I think he is asking if PageRank is still the most important factor in determining where a page ranks in the SERPs

Yes, exactly.

Sorry Lisa and mike you misquote me.All I said Was that it was because of the PageRank factor that Google had an added advantage over Yaho or Msn.Wy would people prefer Google when they already had the other two.For SERP'S you need traffic,keyword relevancy and a good SEO score.I might be new here but am into SEO since the last 14 months.