After seeing Pex in action at PDC 2008 I have caught the fever.
Since then, I gave it a whirle on my own and was pretty impressed. So much so, I chose it as a topic for one of my So-Cal Code Camp talks in January. Got some very good questions and concerns regarding the capabilities and place of Pex in the world of software development and vis-a-vis TDD.
Update: After more than 5 years, Pex technology is now available as an “automatic unit testing” feature in some editions (paid) of Visual Studio 2015