Yes, I have built a commercial "line of business" application on ASP.NET MVC 1.0. We started development on the site when the framework was in beta; and released the site this summer. We are completely happy with our technology choice. Unfortunately I really can't say much more, as my employer would not welcome it.
I'm not sure about the OP's intent; do you mean to get validation of the MVC pattern for very large codebases, i.e. 200 kloc or larger codebases? I can't give you that, and I doubt anyone else really can right now, because there simply hasn't been time to develop so large codebases since the release of ASP.NET MVC. I would suggest researching MVC in Java, as this is probably where you'll find most older & large MVC deployments.
My usual counterargument to the 'very large codebase' fear is you simply shouldn't design so large monolithic apps anymore -- break up the responsibilities and use a SOA architecture to reduce complexity for each individual area of responsibility.
For a webapp on the .NET stack I'd select ASP.NET MVC again with complete confidence. That said, there are many other good choices in webapp frameworks these days.