I know that google doesnt update their PR on their toolbar too often, but the PR is still there. If you get a link from a high PR site, how long until it affects your page in the rankings?
I heard that google updates Toolbar PR every 3-4 months. If you get a link from high PR, you have to wait for next update to see changes.
Google is continuously updating pagerank. It's noticeable by increased or decreased traffic to your website.
You get some link juice immediately but I don't think the full value of the link is given until it is about 5 to 6 months old. I think this is done to prevent people from spamming to receive a quick boost in the rankings