Yesterday I released Newsletter version 3.2.3. It contains a few of fixes and finally a definitive way to integrate with WordPress user registration.
Note! Newsletter still works as standalone subscription system, integration with WordPress user registration is only an optional feature.
More on how the integration actually works, how to import WordPress users as subscribers, how to send them a confirmation email if needed can be found on this page.
Developers will appreciated that now the subversion trunk is the working copy while the stable version is tagged so the real history of versions will be available. My laziness.
Other changes are documented inside the readme.txt file of the plugin.