I must say that PR effects the traffic on your site because it is obvious that if you will see better PR, you visit that site and this increase the traffic on your site.
There has been some confusion on this topic. But I think even though you don't have good Pr you still get a lot of traffic. One of my blog which has PR2 get more visitors than PR3 blog.
Pagerank doesn't effects on Traffic Ranking. I have seen too much sites which have PR0 but ranking by many keywords show at Google top 5 results.
There is no effect of pr on Traffic. Its all depends on Content and promotion. if you want good traffic then frequently update your blog and participate in social media. you will get traffic..
I agree that contents and development are the life of a site and brings enormous traffic to it. Still PR matters a lot as some SEO Engineers or Web Masters prefer high PR directories and submission sites for good SEO from their point of view.