I got my macbook pro a few months ago and this is a problem i've been having almost as long.
I can be scrolling a fully loaded webpage and in the middle of scrolling down it, it just freezes up completely and starts beachballing on me. And at least once a day, when clicking a link it tells me its not responding and i have to force reload every page.
I also have problems where it won't load a page and i have to enter the url many times or even close the tab and try opening it in a new tab before it will load.
I'm on Safari 6.0.5
iOS X 10.8.5 Mountain Lion