Apple today announced the beta release of Safari 4.0, and it’s promising blazing fast browsing, for Mac or PC users.It has a new “Nitro Engine,” that Apple says executes JavaScript up to 30 times faster than Internet Explorer 7 and more than 3 times faster than Firefox 3. (Side note: Firefox is THAT much faster than IE7?) It also loads pages about 3 times faster than either browser, according to Apple.Other new features:• Top Sites: Safari 4.0 tracks your favorite sites based on your browsing history and