I just released some work on the forums to allow anyone to subscribe to a topic. Once subscribed, you'll receive email notifications when a new reply is posted.
You can unsubscribe anytime, or see/unsubscribe from all on the new notifications page at http://www.pedalroom.com/notifications (works only once you're logged in), which is also now linked to from your control panel.
Let me know what you think and what else you'd like to see. I'm also working on things like a quick reply for the forums (which is tricky due to the image uploading) and some other nice improvements. Cheers!