IIS 7 amongst other things is a ground up re-write. The features that really stood out for me were as follows:
- Modular / componentized – use the web.config to enable modules (FTP etc…).
- Management – mgmt console improved, centralized admin, dont require machine privileages, UI can be extended.
- Diagnostics – real time server info, can extend logging.
- Security – Reduce attack surface, manage sites and applications without admin privileges.
For more information go to http://www.microsoft.com/WindowsServer2003/iis/default.mspx