The new site supports notifications, but they are not on by default. To get an e-mail when someone replies in a forum topic or a particular story is updated or commented on, you need to enable notifications. You do this by clicking on "My Account" and then on the "Edit" tab. Scroll down to the bottom of the page to the "Messaging and Notifications Settings" and set things up there.

Note that you can get notifications immediately, hourly, daily, weekly, etc. whatever works best for you. You can get them as HTML e-mails, plain text e-mails or simply as private message notifications within the site itself that will show up when you log in and click on "Messages".

You'll see links like "Subscribe to: this post" below various things and clicking that will get you notified.

You can manage your subscriptions under the "Notifications" tab on the "My Account" page, allowing you to easily remove topics you don't want to follow anymore.