Is URL rewriting really needed?
A scenario that URL Rewriting solves nicely is that of multiple subdomains being routed to a single machine. For example, the IIS URL Rewriting module can be used to have your browser display http://app1.example.com/ or http://app2.example.com/, and the server will treat it as a request for http://content.example.com/app1/ or http://content.example.com/app2/. This is much, much easier to pull off with IIS URL Rewriting than with ASP.NET Routing.