I see the key advantages of MVC as:
- Much cleaner and simpler architecture. No more guessing which event you have handle to hook up your data correctly. No more having to insert a hook to "fix" a data binding problem because the framework doesn't do exactly what you want.
- The framework doesn't get your way as much.
- Decoupled architecture makes much more of the code more easily tested.
- More closely aligned with the architecture of the web. For people coming from a WebForms background this may not seem to be an advantage until you embrace it and design for it instead of trying to write WebForms-like applications in MVC. Fortunately, I had explored Ruby on Rails some before using ASP.NET MVC and had already started to write my WebForms apps in a more RESTful way.
- History/Ubiquity -- despite the fact that Microsoft is just rolling it out, MVC is a well-known and highly respected pattern. It's widely used for lots of web applications in many frameworks. Learning MVC will give you a leg up if you need to switch to a different technology where they are also doing MVC -- say RoR or Java/Struts.
The disadvantages:
- Microsoft's implementation is new and not as mature.
- Few third-party "controls"/plugins for round-trip use -- generic grids and such, though there are lots of plugins on the client-side via jQuery.
- Requires unlearning some paradigms from WebForms to effectively use it.
- The framework doesn't do as much heavy lifting for you; you'll have to learn some Javascript and write more client-side code because the framework won't inject it for you.
