Wow! Going to have to check this out! Perhaps I can postpone my Tiger update a wee longer! And maybe I can start using Safari again now that it supports HTML WYSIWYG editing (assuming it works with the blog systems which I use which may be a bad assumption).
What you are getting is all of the new standards support, new WebKit capabilites, site compatibility fixes and performance optimizations that are also present in Safari 2.0 for Tiger. The layout engines for the two are virtually identical.