I have just set up a multisite network, and have installed this plugin.
Everything appears to work great after I checked the "enable tags" option in the sitewide tags setting. (this is not entirely clear).
The only problem I now have is that in the box where I select which blogs to post to, every blog is called "main multisite". I haven't given this name to any of the blogs on the network so I'm not sure where this has come from.