Developing Front End in ASP.NET

We have a developer who would like to develop their web site using ASP.NET for the front end, but have all of the data stored in AgileApps. And use the native AgileApps user interface for the administration of the web site.

This is really an alternative to using the Sites functionality within AgileApps to build out a custom web site.

Are there any issues with taking the approach of using ASP.NET rather than AgileApps Sites?

Has anyone else done this?