You are right that PR is not 'the be all'. You shouldn't worry too much about it and should really be focussing on other more important factors.
Pagerank (or PR) is really just a mathematical formula, which you can read more about here. In order to get a larger ranking, you essentially need links from pages with higher PR. For example, if you wanted to obtain a PR of 2 you would need 3 links from a PR3 page. You can find various charts around the web that highlight PR requirements.
Having looked at your site in opensiteexplorer.org, it is clear why your PR is not higher. Although you have over 1,500 links, these links are from only 12 different c-classes. This essentially means that you only realistically have 12 different links due to the way Google treats links from the same c-class. Also, as Darin has rightly pointed out, the majority of these links are pretty poor quality with not much PR themselves.
If you are adamant about improving your PR, you will need to obtain links from sites/pages with a higher PR. However, I wouldn't recommend adopting a strategy based on improving pagerank. You would be much better off improving the quality of your site with content that people find useful enough to link to.