To add the column of results from Safari 4 beta, you can cut and paste the second URL (Safari 4 results) into the field labeled "To compare to another run..." and press Enter while inside that field. The hyperlink "Run Again" at the top of the results page will run the SunSpider benchmarks in the browser you're running at the time.
The test platform is a 2.53GHz MacBook Pro with 4GB of RAM running Firefox 3.0.5 and Safari 4 beta, both Universal binaries in x86 mode.
The distilled SunSpider results number is handy, but like most benchmarks, it does a poor job of telling the real story. Individual test results range from 1.17x to 16.4x. Users' mileage will vary according to the application, but I'll offer some clues to the more meaningful results.