Since picking up GTD in January I have evaluated many PIM tools on the Palm, PPC, and PC. My last big adventure was with Excel, but currently I am having even more fun doing GTD in Ecco, syncing to an NV-70 Palm (Clie). It is hard to see how anything is ever going to beat Ecco as an awesome tool for GTD! It is now available for upload online at:
Download Setup32.exe, and this will install version 4.01.1, which the latest version. All files created with earlier version will work with it.
Ecco is an incredible PIM program; it's been described by many users as "addictive". Despite being discontinued in Aug 1997, it still runs great on Windows 98, 2000, XP, etc. and there are many active users. The Yahoo!Groups "eccopro" forum has 850 members and is quite lively. Once you get the 'Gestault' of Ecco and get your business onto it, it is really fascinating how much faster you can work, and how much more output you can have -- I've never seen anything like it. I'll be surprised if it doesn't get revived either as open-source, or an ambitious startup company over the next year or two - considering the mometum and fan club base.
There has already been one GTD Template for Ecco published (see the archives), I'll also be publishing one soon.