As we've been saying at Mozilla for ages, measuring users' security is much more than just counting bugs. Today, those guys who have done the most for publicizing bug counts have released some data about actual software installations and their vulnerabilities to vendor disclosed and patched exploits.
What Secunia found when looking at web browsers was that Firefox users were the most up to date of all, with IE 7 just behind Firefox 2, IE 6 pretty far behind that, and Opera users the least up to date of all.
Firefox's Application Update System has been a huge piece of work over the last three years and this study is a good validation that we're on the right track, beating even the Windows Update system.
AUS offers both patch updates and full updates for Firefox on Mac, Windows, and Linux across 40 languages, to our installed base of more than 100,000,000 users. It's an amazing system built by some of the smartest people on the planet and it's working.
No web-connected applications should be without this kind of update system. Not providing your users with timely automatic security updates is just irresponsible.