As you may know, I'm a reluctant switcher from Mac to Windows. I am also a fan of GTD. I had been using Jello Dashboard (JD) to implement GTD under Outlook. JD is a very nice system, the developer is friendly and responsive, and I had even written several patches to adapt it to my way of working. I was even in the process of drafting a series of blog posts titled "My GTD under Outlook setup".