Today's Preview 3 release of ASP.NET MVC includes a bunch of improvements and refinements.  We are starting to feel good about the URL routing and Controller/Action programming model of MVC, and feel that those areas are starting to bake really well.  In future preview releases you'll start to see more improvements higher-up the programming model stack in areas like Views (html helpers, validation helpers, etc), AJAX, sub-controllers and site composition, deeper Login, Authentication, Authorization and Caching integration, as well as data scaffolding support. 

I also have a (very) long tutorial post that I started putting together this past weekend that walks-through building an application using ASP.NET MVC Preview 3 that I'm hoping to wrap up and post in the next few days.  This should provide both a good intro to ASP.NET MVC, as well as help provide some context on how all the pieces fit together if you are interested in using the ASP.NET MVC option.

Hope this helps,

Scott