I'm interested in learning python to have access to a more agile language for writing tests in my .NET projects. 
Is IronPython mature enough for these purposes yet? I'm content with writing tests in C#, but find dynamic languages like ruby and python very attractive. Would it be better to forgo IronPython while learning, and stick to the official version 3 distribution? 
I'd be interested to hear from anyone that has had success writing tests for a .net project in ironruby or ironpython.
Edit: reworked my question to address the real issue about using dynamic languages for TDD in .NET - the version issue isn't as important. Apologies for the poorly worded question.
What I've found however, is that IronPython to the best of my knowledge appears to be based on Python v2, while many of the learning resources available on the web are focused on Python v3.

I don't know what resources you've been looking at, but the majority of them are for v2.
Learning Python on Windows for TDD