Stop using pagerank its so outdated that the ranks aren't even useful anymore. The real pagerank could have changed dramatically since the last update. Use mozrank instead. Much more accurate. Ranked from 0-10 as well. If the page has a moz rank of 9 then its pretty much like having a pr 10.
Yes, it's been a while since the last major Google PR update. Like what you've suggested, maybe it's time to change focus to Mozrank.
I'm not sure about how Google detects that any link is coming from 3 way link exchange or by buying the links.......