As most of my clients come via word of mouth or from local advertising the PR of my sites don't matter too much.
If the methods for increasing the PR is against the rules of the Google, then it should not be followed.It may result in penalty for the site.So, its better to use the organic way to increase the PR.According to the Google Panda update, quality is an important thing for getting better indexing.So, PR is also important as the PR of the site is dependent on the quality of the content of the site.We can follow both On page and Off page for getting higher PR for the site.