I'm hosted on an IIS6 platform. I turned caching on, but no pages have become cached. The telltales ("super-cache" verbage in the page source) or files written to wp-content/cache are missing. Thus, nothing is happening. There are no error messages, except there is a warning that my wp-content permissions are set to writeable, and I should fix that with a chmod 755.
I'm using the PATHINFO "almost pretty" form of permalinks (because my site crashed when I tried to add/use an .htaccess file).