What does IISReset do in addition to recycling all Application Pools?

And are any of those things not programmatically available (.Net) from Microsoft.Web.Administration?

Solution 1:

When you recycle an application, the worker processes (w3wp.exe) are shut down and new ones started.

When you perform an IIS Reset you restart the following Windows services:

IIS Admin Service

Windows Process Activation

World Wide Web Publishing

The worker processes depend on these services, so naturally ALL worker processes (not just the ones pertaining to the application you would like to recycle) are shut down, and can not be started until the WWW Publishing is ready to process requests again.