The earlier startups ('76 and '87) gave me the experience of what a startup is like. I _was_ the warrior god. I worked 60, 70, 80 hours per week. I _knew_ I could overcome all. In one case it worked, and in another it failed.
By relfecting on those experiences, and many other experiences in companies large and small I have since learned a great deal about programming; and about human nature. One of my greatest realizations is that you cannot go fast by rushing. Every shortcut you take slows you down. Every attempt at cutting corners, adds more corners. And so I adopted the mantra: "The only way to go fast is to go well."
In 2002, when I started the FitNesse (fitnesse.org) project, TDD was the rule. I didn't know how well it would work, because I was very new to TDD at the time. But since the risk was low, I gave it a shot. It succeeded beyond my expectations, both as a programming discipline, and also as an open source project. The power TDD gave us (and still gives us) to keep the code clean and under control is something I'd never experienced in any other project. It was profound. It was powerful. It allowed us to go fast, and _keep_ going fast because the code stayed clean. I have come to view it as a moral imperative. No project team should ever lose control of their code; and any slowdown represents that loss of control.
I have since consulted on many projects using TDD, and have helped many others to adopt it. My son, Micah, who was the lead programmer on the FitNesse project, continued to practice TDD in other projects for clients of my company, with great success. When he founded his own company, 8thLight.com, TDD was a founding principle.
When it came time for me to start another company, (cleancoders.com) TDD was, and has remained, a founding principle. TDD keeps the code under control. That control keeps me going fast. I can't imagine surrendering control of the code ever again.
There's an old saying: "Your true beliefs are exposed under pressure." I'm glad your AgileZen story had a happy ending; but I think you got lucky. When the pressure came, your true beliefs came out, and they did not include TDD. You abandoned the discipline because you thought it was slowing you down. And now you are communicating that meme to the world at large. That's a shame.
As long as someone thinks TDD will slow them down, they will abandon it whenever the pressure is high enough. I, on the other hand, know that TDD speeds me up. So when the pressure comes, I hold to my discipline.
I know I can't convince people that TDD will speed them up. But as I look out over the industry from my rather long perspective, I see the change rolling across it. TDD was unknown in 1999. It has gained in awareness and adoption every year since that time. The momentum continues to build.
In another 10 or 15 years TDD will likely be as prevalent and important to programmers as hand-washing is to surgeons or double-entry bookkeeping is to accountants. I stand a good chance of seeing that happen.