As a word of caution, I want to mention that users of alternative browsers may not like this story. If a new benchmark tool is to be believed, when it comes to Rich Internet Applications (RIAs), Internet Explorer performs better than Firefox and Opera on Windows XP, and Safari performs better than Firefox and Opera on Mac OS X 10.5. Furthermore, Internet Explorer on XP beats Safari on 10.5. The latest final versions (read: no IE8, no FF3, no Opera 9.5) were used in these tests, which were created by interface developer Sean Christmann.
(Follow to source to see graphs)