I wrote about Tracks in an earlier post
on my blog. Tracks is a Ruby on Rails GTD application that does take some getting working. I have not yet looked at any GTD applications as I want to finish the book and start on my GTD process before I jump in at the deep end playing with the eye candy applications.
Anyway, super review of the application over at the Cranking Widgets
website that sure is worth a read before you spend the time installing Ruby and Rails to get Tracks working.