Not really - not for ranking for specific pages for specific keywords, especially if the lower PR page has a good link campaign behind it.
Also, newer high PR sites are far less likely to be able to rank for their target keywords than lower PR but older websites. I think the whole authority issue has really underlined the issue.
I have seen plenty of examples myself - for example, I had an old site in a certain news niche. I set up some free directly links, then decided the branding was crap, so set up a better branded keyword domain and set up some very strong links to it.
The older site with PR1 still outranks the newer PR4 site for the keyword. And that's on the main index page, rather than a niche internal page.
Seriously, PageRank isn't really worth worrying too much about. Sure, it's a great badge to wear - I was chuffed when Platinax when to PR7 - but even still, its traffic has been flat all year when it began as PR5.
I would always recommend looking at sales and conversions and niche traffic levels over PR anyway.
2c.
