Ok!! So everbody and their mother have already blogged about the new MVC Framework released with Asp.Net 3.5 Extensions preview 1 week ago, but i just got time to try it out. Its pretty different from the WebForms model, and is not meant to replace it in any way. Its an alternative that promotes test driven design and makes it easy to unit test your code. As per ScottGu, it enforces a clear separation of concerns within applications. In other words, it makes it harder for the developer to make bad design decisions, because it encourages you to keep your layout (view) separate from the data access code (model) and business logic (controller). Also, the URLs in an MVC point to the Controller and not to the view, so it gives you much more control over the URLs in your application. You also do not have the file extensions as part of the url by default, since you are pointing to the Controller class, and you can specify the method (ControllerAction) to call along with the parameters in the URL itself. The controller invokes the appropriate view which renders the html.
To learn more about Asp.Net MVC framework, check out the following resources:
Its quite a handful for a 1 week old technology preview framework, isn’t it!!