My quote-of-the-day, regarding Test Driven Development:
I am convinced that it [TDD] can work to your benefit, but it’s not without a price (time to learn, time to implement, and more). It’s definitely worth the admission price, though.
Taken from the excellent The Art of Unit Testing: with Examples in .NET by Roy Osherove.
Mark Cooper 
Hehehe, the post i’m preparing says exactly this (with other words). Easier things tend to get more adoption. The easier TDD gets, more and more adoption it will receive.
I think the Test Frameworks out there can help make it easier, but i just think that for some big issues the programming languages themselves should add some core features to enable an easier approach. It should be something integrated on the programming language. For example, the existing comments support that (almost) every language has. It is not something that drives or changes the code execution flow, but it is something that adds value to it. Unit Tests should be the same, the programming language should have a native support for it, especial tags/keywords/instructions/blocks that should make it easier to implement TDD.
Nice link btw, i’m already looking at the book sample.