I just upgraded to the latest version of the plugin, 0.9.6, and caching is no longer working. I tried deactivating and reactivating the plugin, as well as deactivating it, deleting the cache directory, and reactivating it. I also checked the .htaccess files as recommended in the readme.txt file, and none of these things worked. Caching was working fine earlier today before the upgrade. I'm on WordPress 2.8.2, and have been for about a week.