Nightly webkit build = double speed of your Safari
According to this article on anandtech
the latest nightly build of webkit doubles the performance of safari scrolling on retina macbooks. It in fact improves the scrolling even on my good old 2011 macbook air significantly. Verge homepage is smooth as butter and even articles with a lot of comments (like the iPhone 5 review) do not slow it down to a crawl.
Bottom line - its incredibly faster, like night and day and everyone should use it :)
Just use it instead of safari, it will have all your preferences and extensions your safari is using right away, the only difference is the golden icon.