I've just installed Google XML Sitemaps plugin for one of my networks that I'm playing with and when I activate it I get a message that says:
Google XML Sitemaps is not multisite compatible.
Unfortunately the Google XML Sitemaps plugin was not tested with the multisite feature of WordPress 3.0 yet. The plugin will not be active until you disable the multisite mode. Otherwise go to active plugins and deactivate the Google XML Sitemaps plugin to make this message disappear.
I'm assuming that this is being done by the makers of the plugin until they have a chance to verify that it plays well with 3.0. Has anyone seen this message with other plugins?