Version 7 represents a major change to the underlying design of IIS. It has been designed to be heavily modular with "over 40 pluggable modules" that can be replaced with either native or managed code.
Instead of using the metabase, IIS 7 uses XML based configuration files similar to those used by ASP.NET. This allows for XCOPY style deployment of both code and configuration for web sites.
In addition to classic ASP and ASP.NET, there is support for many third-party frameworks including PHP, PERL, ColdFusion, and Ruby.