PR is an unreliable matrix or platform on which to measure any site by, one could link to a useless and only slightly related site from one's own network of P5/6/7 sites and that site will gain PR5/6 in few months*** even if it has hardly any content to write home about. However, PR7 upwards is considered "elite" and are more likely to justify their rank and their traffic which also is usually consistently high, so is their backline profile. Some but not all PR5/6 sites maybe the same. Having said that, there are many sites that are PR4 that are more successful than PR7s and have more authority and traffic than them on various niches, depending on how highly sought after the content / information is.
I came across many PR5/PR6 sites, their PR was bogus, if I were to fall for the trap of saying wow a PR6 site for sale, I would've spent $$$$$s IN A TEMPLATE site linked to through temp or permanent high PR OEN SITES redirects just to give it that PR to achieve high return in selling it, then the redirect is pulled down and put on another site and so on, many do it as a lucrative quick money making scheme. The conclusion is PR alone is complementary to other factors that are easily measurable, solid themed organic backlinks, traffic over time, age of site and its content, membership and circulation etc.
There is one plus though, if the backlinks to the site were organic and were not from your own sites, it is a step in right direction to stepping up the ranking ladder, you must be providing something worthwhile people want to bookmark it and link to it, so keep it up!
*** this will usually result in a filter or penalty in the end in my experience and that of others, and is discouraged, seen as excessive and unwarranted cross-linking to manipulate rank which G* frowns upon.
OK, let's keep this thread about updates and SERP changes, which by the way there are SERP changes and peculiar updates in the last few days.
I have a feeling most caffeine DCs are turned off and the old DCs were put in place, the problem is the old DCs are lacking most of the index count it seems. As though most database records were moved to the new infrastructure, which explains the SERP links count when doing the site: operator, only 20-30% are present on the old databases, the rest is on caf DCs. Either G* has a massive problem rolling Caffeine altogether or we are just about to witness the much anticipated Roll out. We've seen this kind of behavior pre Florida and pre Bid Daddy amongst other major updates, total chaos, the calm before the storm, then the colossus twister! If I am right, a press release or blog post is likely imminent in the next few says from G*!