Send me site updates
That's the same as the notify me of posts for users who are not logged into WordPress.com.
Subscribe to Comments hasn't been updated in 2.5 years. The comments page on the author's site is somewhat out of control with spam and no answers to recent questions. Is it really the best option out there?
I also saw the Subscribe2 plugin, I'm reluctant to get involved in code that is half free, half for sale. Plus, I think it's really important that both comments and posts are integrated so users can one-click unsubscribe from everything. I believe that's how it works on WP.com.
I think most of wp.com is open source, but there are pieces they keep for themselves, I've run across that before. I'm guessing at this point I'll build something on top of Subscribe to Comments, it seems like the best starting point.
Thanks for taking the time to share MacManX.