ACWOLF Doesn't hurt my mind!
Most other ToDo / GTD programs are either inadequate at really organizing much and being scalable, or they hurt my head. iGTD has prospects as far as future versions, but it really just doesn't work easily and mindlessly, it takes a lot of patience to simply focus on the interface. OmniFocus looks great, and would probably be my choice if not for Things. Midnight Inbox, Ready-Set-Do, and others like that are designed to train you and help you build habits, but once those habits are built, those programs don't get out of the way enough.
Things is the only program that really gets the concept right. It's like google vs yahoo. Yahoo works and is continually updated, but it still is overwhelming and complex. Google realized how to make the overwhelming internet be viewable through a simple interface that does not overwhelm you. Things does that for your life and tasks. It really promises to far surpass any other GTD type program out there.
(Version 0.8.6)