I'm disappointed to discover that this plug-in only seems to work spottily. I have several friends who are helping me test it, and while a few have received the notifications they've subscribed to, it seems that even more have not. I've checked the "Manage Subscriptions" page and have confirmed that they've subscribed correctly.
Also, as administrator, I'm only receiving notifications to about half of the new comments. (I have this same problem with the notifications I should get directly from WordPress. Interestingly, the missing notifications from this plug-in are the same ones that don't come in from WordPress; I either get both or neither.)
I also personally subscribed to all from a different email address, and am not getting notifications for most comments.
I was really hoping this would work. Looks like I'll go back to sending notification emails to commenters by hand.