You can use it on your multisite, but have to think how you want to use it. It registers the users per website when you install it on every site. This means sending also per site. I liked to have central control so added a extra ‘news’-site (easy on a multi 😉 and collect al subscribers and listpreferences there and also send out letters from there. For including the latest newsitems you can use a post-duplicationplugin.