I spent quite some time adding user roles to our product on Sunday... and today MSDN posts a nice article showing how much easier it is with ASP.Net 2.0 !
http://msdn.microsoft.com/msdnmag/issues/04/06/ASPNET20Overview/default.aspx
Also the 'Master Pages' concept is something I would really like to employ.
That said, our product is near completion with ASP.Net 1.1, and to take advantage of these changes would take quite some time to reimplement.