I love the fact that I can see projects/subprojects/all actions (active and inactive) on the projects screen, and all *next actions* on their own with quick filtering options on the actions screen. The added option of topics with colours lets me see at a glance exactly where a next action comes from.
I also tried MLO, but I found it needed too much tweaking for the time I had at hand, and just didn't look as pretty

. Then I tried the GTD Outlook add-in, which was fine but also needed tweaking to suit my needs. No time. Then I tried Franklin Covey's PlanPlus. What didn't crash my system killed my Outlook, although I believe most users don't have this problem. Their support is useless, though.
Then I tried Outlook on its own - oh boy, not something I would care to repeat. My 'trusted system' ... well ... just wasn't trusted, bcs there was always something I forgot to tweak in just the right way and it took ages to adapt the program to GTD.
Then there is the action of adding thoughts - I don't want complicated, I want to dump. Outlook Tasks had me thinking 'so under which project/category/, which context' etc., and if I didn't enter everything, I just never remembered to go back and add them. In that sense, TR is also perfect. Dump, then process later.
I wanted a system that would integrate well with Outlook, since I use the Outlook calendar and tasks, so when I first tried TR I wasn't really interested, but after much tweaking and swearing - here I am, and loving it! I now use ClearContext (nice program, wonderful support) to process my email, and TR for everything else. Simple, easy yet powerful. And I love the support!