According to the redmondmag, they're at least mistaken.

The majority of IE's notorious security flaws stem from its pervasive integration with Windows. That is a feature no other Web browser offers -- and an ability that Vista's Protected Mode intends to mitigate. IE 7 obviously won't remove all of that tight integration. Lacking deep architectural changes, the effort has focused instead on hardening or eliminating potential vulnerabilities. Unfortunately, this approach requires Microsoft to anticipate everything that could go wrong and block it in advance -- hardly a surefire way to secure a browser.

The typical MS approach - instead of fixing fundamental design flaws, just tack on more crap 'til it looks like it works again.