I've used several tools, and this one definitely tools my list of newsletter apps. Their support forum is super responsive. It's fast, simple and complete. It's totally customizable down to the send rates and times. Pre-loaded templates make it easy to keep the look fresh and your subscribers interested.
Using the software despite its few bugs has been great!! The only issue I had was getting the cron job working. Later discovered it won't work with J1.7, which I could set a bounty on getting that done.