Creates four rss 2.0 feeds showing recent posts, comments, pages, and one combined [posts and pages] from all blogs. Works both on WPMS, and WPMU
Only if you install WPMU/ WP 3.0 as subdomain installation when you installed WordPress, you will be able to have feeds like "yourdomain.com/full-feed/". When you install WPMU/ WP 3.0 into a subdirectory installation, your feed url will be something like "yourdomain.com/subdirectory?wpmu-feed=full-feed".
wp-config.php should have either of the below constants defined and set, in order for the plugin to detect its a subdomain installation.
You must disable your cache plugin to cache the feed as a static page. If you are using W3-Total-Cache plugin, add your Feed URL (relative path): to the Never cache the following pages: section under Page Cache Settings. Ex. "/full-feed/" and make sure to clear empty all caches.
The reason is your cache plugin makes the cache of the feed [which has a Content-Type: application/xml]. But after it is cached, when the browser requests, your cache plugin deliver the already cached static file, which now is delivered with Content-Type: text/html]. Some cases, this causes the RSS Widget to not to recognize the feed.
I know its out-of-date. I kept the original codes and cleaned long time ago. I should probably remove WP Object Cache in the next versions. Please suggest a better way on my blog Ada WPMS Sitewide Feed