There is one feature coming with IIS 7 (http.sys, as such it is more an OS feature) that I have been waiting for a long time: being able to see what's in the kernel cache! The key to this new supercool feature is the netsh command:

C:\Users\Administrator>netsh http show cachestate ?

Usage: show cachestate [[url=]<string>]

Parameters:

    Tag       Value
    url   -   Fully qualified URL. If unspecified, implies all
              URLs. The URL could also be a prefix to registered URLs

Remarks: This command lists all resources and their associated properties
         that are cached in HTTP response cache or displays a single
         resource and its associated properties.

Examples:
      show cachestate url=http://www.myhost.com:80/myresource
      show cachestate

Some information can be obtained in the article New Networking Features in Windows Server "Longhorn" and Windows Vista (you can even flush the cache), and here is how it works if you browse to the default Web site of IIS 7:

C:\Users\Administrator>netsh http show cachestate http://localhost

Snapshot of HTTP response cache:
--------------------------------

URL: http://localhost:80/pagerror.gif
    Status code: 200
    HTTP verb: GET
    Cache policy type: User invalidates
    Creation time: 2006.3.21:23.30.16:0
    Request queue name: DefaultAppPool
    Headers length: 187
    Content length: 2806
    Hit count: 1
    Force disconnect after serving: FALSE

URL: http://localhost:80/iisstart.htm
    Status code: 200
    HTTP verb: GET
    Cache policy type: User invalidates
    Creation time: 2006.3.21:23.30.14:0
    Request queue name: DefaultAppPool
    Headers length: 233
    Content length: 774
    Hit count: 1
    Force disconnect after serving: FALSE

Tracking caching behavior will be so much easier.