I wonder if it works now. Last time I tried it, you could'nt switch back from the preview tab. In fact you couldn't switch back to anything, nor click any button. And that was the 1.0 release, ready for production. It put me off a bit.
Nowadays I leave the web design to people who know more about it than me. Then I take their
mess results and make it standards compliant by hand. After that I feed it to my cms...
I think nvu is a cool thing though, because it works on linux. People should try and see if this isn't enough for what they need to do. No need to buy expensive software :-)