Please tell me that PR effect in optimization or not. if i have high PR than can i get better ranking than Low PR.???
you can't say it has nothing to do, it's just not the most important factor or not the only factor, but of course it has some importance
All things being equal a site with higher pagerank will outrank a lower pagerank. The fact that so many components are taking into account for the algorithm to score a rank a website means that this is unlikely
IMHO, pagerank is based on incomming links which are relevant in SE positioning so the higher the PR, the better you should rank. The ranking algorithm is quite complex, but I'd bet PR is factored in somewhere.
PR itself isn't a factor. PR indicates the number of incoming links which in itself is a positive factor. I cant believe some people here never gets this simple fact.
Since PageRank is a measure of number and weight of incoming links, to say that PR is a factor in Google ranking is a shorthand way of saying the same thing. Those like you who inisist on confusing the issue with these rather pointless and meaningless distinctions are not doing anyone a favor, especially not people new to the whole concept as seems to be the case in this thread.
Yes, PR is still important, or let we say, the collection of incoming links that you have. But it isn't the only factor. You can have an optimized PR3 beating a PR5 site. There are other important factors at stake.