Cassini too limited? Ever find yourself frustrated because you cannot apply and test security features, or certain configurations with the web server tool that comes with Visual Studio. I have several times found myself having to install IIS on my development machine. I know many corporate environments prohibit some developer groups from having IIS installed on their machines for several reasons.
IIS Express now combines the best of both worlds and does not require an administrative account to run. IIS Express will also have integration into Visual Studio development so you can still get F5 (debug/run) experience. Read more here