We are about to embark on a large enterprise application. I am seriously considering using ASP.NET MVC because:
My opinion: use ASP.NET Webforms.
Disable ViewState in the Web.Config.
There is no need to preserve state because everything you really need is in the Request object. Use Javascript in conjunction with AJAX for data retrieval to render your UI controls client-side.
Create serverside wrappers in the form of control tags for your client-side component renderer. This is how I've been working for ages now, and it's fast, reliable, testable and organized.
It does take some time to setup a decent framework for this working method, but eventually it will rule.
I rather have no spaghetti code like MVC. Been there with PERL/PHP and classic ASP.