I would agree that the last PR update was quite odd. We’ve seen several people post here that have done little work (my assumption) and been awarded PR5. For our site, it seems the PR update hit some pages and completely missed others. We have pages that have been on our site for over 6 months that still have PR0, while other pages that were thrown up a couple weeks before the PR update have PR4. IMO, someone at Google messed up the last PR update, and it won’t be until the next one until everything is fixed. Hopefully the real PR that runs in the background is working properly.
Matt Cutts has alluded to the possibility of another PR update right away, rather than the usual 3+ month wait.