If that's the case use tools such as wordtracker's to see if the keywords that you're targeting get enough traffic. You could also be competing on some keywords where your competition has a higher PR. Or possibly the customers you want simply don't think to use search engines to find your type of service. What percentage of your traffic comes from search engines?
I've looked at Google's Keyword Tool and tried a bunch of different possibilities. There are certain keywords I'm targeting but despite my PR5 pagerank, I'm not at the top of the page on these yet. So it's a slow move forward. Still people continue to write about FBA so I expect this is a long term investment. As my site gets more quality links and longevitiy, I expect one day I may see more search traffic for the terms I'm targeting. Just not yet. A lot of the search traffic I get is people searching for feedback army by name. I take this as an encouraging sign about awareness of the product itself.
I think that is good as well. Generally a large portion of my traffic is direct traffic. Most visitors when they discover my site have a need to generate a email address, but the next day or later that afternoon many will go directly to my url. I typically see a spike in users the day after i see a spike in traffic. All this SEO stuff can certainly take a long time and not seem to be paying off, FBA seems like a great service that I would like to use in some upcoming usability reviews. Just hang keep up the good work, and one day you'll be #1
Did you check the search volumes for the topics you cover? Did you look to see that your content includes the most popular keywords for that content? Do you have a lot of content? PR is just a modifier... you still have to have the things that people are searching for for them to come to your site.
I'm working on the content. I have a blog on a subdomain which is just PR3 right now. The blog of course is more diverse with the content. I wrote a post about once a week and put some time into what I write. I'm giving it a year (started in Jan) of posting once a week to see what effect it has. Just from the few posts that have done well, it has been worthwhile so far.
I'd say that SEO and page rank are good things to have but they're not going to be sole (or majority) drivers of traffic for everyone. So it's good to think about other forms of marketing too.
I had a period of time where I was very interested in SEO. Mostly because I thought I saw an easy path to more traffic and more sales. I put some time and effort in (keyword picking, optimizing parts of my site, blah blah) and saw some changes but nothing I'd consider too worthwhile. This led me to where I'm at now, focus on content and let the rest happen.
