As far as I understand, you should have a single URL to access a given page on a website to prevent duplicate issues. With this in mind I have setup IIS7 Rewrite to point my friendly URLs to my .aspx pages. e.g.
/category/widgets/ has a rewrite to
Should I allow either of these URLs to resolve my web page, or should I also 301 redirect
/category/widgets/ so that there is only a single URL that resolves the page?