The plug in works great with the basic functions. Unfortunately it is not possible to manually set the localized language. Many text-fields can be set manually, but not all. E.g. the validation texts on the subscription form is set automatically from the user interface of the WordPress administration language. The same goes for some contents in each newsletter.
So, if your like me, and want the WP-admin GUI in one language, but wants the contents of your newsletters to be in another - this plug in is not for you. Too bad, apart from this it seemed really good.
And unfortunately I cannot agree to the other reviews stating that the Support is good. I would have expected the reaction "wow, that's a great feature request, I'll try to get it fixed". Instead the support told me "I'm confused."