I started to use ASP.NET MVC, and I have to say, it's incredibly easy to learn and use. Development time is cut with at least 30-40% and I can spend more time on implementing the business logic and data access.Routing is another thing that have been improved, instead of using pure query strings, you build routes. This enables you to build clean URLs in a very simple way. As a ex. you would write a link as /Blog/Edit/4232 instead of /Blog/Edit.aspx?id=4232.
You had the capability to do routing before MVC, but MVC simplifies it alot.