I tried em all. I have to say, I like a configurable, flexible system. I found something the other day that blew me away as far as ability to implement GTD. The app is called Memento. I promise you that I am not the vendor / developer / or any other way tied to this app. I just like the ability to create my own custom data structure for keeping track of stuff. When I found this, i realized that I could create a mini-CRM and tie it together with a GTD system together in one app.

Memento is the app. I emailed the vendor and asked him about future enhancements and I was happily surprised that most of the things that I asked for (custom icons, and other requests) were already on the list for the next or future releases.