We are starting off a new project with sitecore as our CMS. I was thinking of using Sitecore as the Content Authoring Tool and use ASP.net MVC as in the Content delivery(CDA
I know that Sitecore developers have considered ASP.NET MVC, but I don't know if they've tried it. I can't think of any Sitecore projects that I think would have benefited from ASP.NET MVC. The Sitecore dynamic response engine, pipelines, handlers, wildcards, and other features seem to provide a superset of what you can accomplish with MVC. Similar story with ASP.NET master pages - you could use them with Sitecore, but Sitecore's layout details are superior.
I'm not against ASP.NET MVC with or without Sitecore, but Sitecore seem to provide the features of a controller (really ASP.NET is the controller, and Sitecore just plugs in), your information architecture is the model, and your presentation components are the views.