ThinkingRock

Very good feedback from users: it changed their life, allowed them to at last implement GTD, best GTD tool they found, etc. On average there are 300 downloads a day (see the stats on SourceForge).

See User Feedback and User reviews.

Personal favourite reviews are:

• 16 July 2010: I really appreciate your fast response and great results...not to mention a killer application.
• 12 July 2010: Goals are a great addition to thinking rock and nicely done.
• 19 June 2010: I bought your software a couple of hours ago, and frankly... well... I wanted to originally write you a long and verbose email about my thoughts on this software. But it's 2:40AM, and I have to force myself to bed, because your software is simply of a rare quality: both flexible and intuitively easy to use. I can't believe I actually considered not buying this because of the 40$ price tag... silly me. Simply the best 40$ I spent this month on anything by a LONG shot, and probably the best spent this year.
  Thank you from the bottom of my heart. As exciting as the GTD method is, as fundamental as its impact was on my life in the last 2 months, I was growing increasingly frustrated with my lack of success at finding a set of tools that would integrate nicely with each other, taking care of all GTD aspects from beginning to end. Well, you pulled it off with flying colors.
• 26 Feb 2010:I am overjoyed at your latest upgrades to the Thinking Rock software, especially the changes to the Notes fields. I cut and paste constantly from other applications, and now I can do it MUCH more quickly
• I just downloaded TR to take it for a test run, and after half an hour I found myself drooling over how simple, easy to use, and well-implemented this program is. I've tried ..(list of software).. and damn near everything in between to try to implement GTD on a computer, and none of it worked as well as your software. I just wanted to drop a line and give you two thumbs up. - from Ben
• I just donated $100 USD...I want to complement you on your wonderful product. This is the only software I found that truly understands the GTD system. I searched high and low for a commercial product (anyone for that matter) and in the end picked yours. Its a product definitely worth paying for once it gets out of beta. Fantastic work! - from Jonathan