This plugin seems to work as advertised. However, I would like it more if it gave subscribers and obvious and easy way to UNsubscribe. There should be an unsubscribe link in every email notification it sends out.
Also, it would be better if subscriptions required verification. A lot of email subscription systems work this way: you enter your email address to subscribe, it sends you an initial message saying "You have subscribed to (whatever it is), please confirm your subscription by clicking this link." This helps ensure that people have entered their email address correctly. It also prevents people from entering someone else's email address and subjecting them to emails they don't want.