Hi Jeepster,
I totally agree with Francisco...guest blogging should only by one element of building links, the fact is we don't know what the algorithm is for a reason (the fun is in the hunt).
I have found if you do a combination of the little things correctly and keep to the basics of web marketing and optimisation, "regular content", social media presence, and good on-site optimisation etc, etc it will go along way!
I recently tested a couple of sites to see what sort of timeframe it would take google to index a page..so I set up "Google Alerts" for certain keywords I wanted to target, the theory behind this I would be able to see how long it takes for google to index and crawl a page and in particular a link. and then measure it against my SERP (search placing)
I tested out the theory on two sites SBWire and PRBuzz, it only took 2 days for it to get indexed and my placing did move not long after, in the right direction 
So to answer your questions, PR's are still an effective link building strategy; however it is all still relative to what your competition is doing ? do they have a strong social media presence, do they blog do they have great content content.
I hope this helped, what does everyone else think ??