But if there are two sites with similar quality of optimisation, the one with the higher
PR is likely to be better placed.
My way of looking at
PR is, never mind the quality, feel the width!
Also, when looking at your relative position - ie "I'm No.1 for xyz serach term, look at the top right of the screen, are you 1st - of about 500 - or 1st out of millions.
But the above comments are perhaps the most relevant, if your site is number 1 and it brings in visitors and contacts and then business, Who Cares!