I installed a new module designed to send email notifications of changed content, including comments and etc. It is opt-in only. If you want to try it out, follow these steps:
1) Click the My Account link in the navigation pane.
2) Click the My Notification Settings tab
3) Enable notifications globally and enable them on the specific types about which you would like to be notified.
This runs on a cron job. The interval is global for the entire site. I've set it at 3 hours for right now. We can bump it up or down depending upon your feedback.