I think Safari 6 has actually got the best UI experience and speed, but it's lack of cookie-handling and privacy controls make it all but unusable. I end up using Firefox because even with the best Safari extensions, you still can't individually whitelist or blacklist cookies to selectively prevent installation of the ones you don't want while allowing use of the ones that you do. Amateur hour.
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Have you tried the Ghostery Safari Extension? It manages cookies pretty well, I think. I've been using it for about a year or so. You can whitelist things.