<p>Has anyone built a website with IronPython and ASP.NET.  What were your experiences and is the combination ready for prime-time?</p>

The current version of ASP.NET integration for IronPython is not very up-to-date and is more of a "proof-of-concept." I don't think I'd build a production website based on it.
Edit:
: I have a very high level of expectation for how things like this should work, and might setting the bar a little high.  Maybe you should take what's in "ASP.NET Futures", write a test application for it and see how it works for you.  If you're successful, I'd like to hear about it.  Otherwise, I think there should be a newer CTP of this in the next six months.
(I'm a developer on IronPython and IronRuby.)
Edit 2:
Since I originally posted this, a
newer version
has been released.