Shined up real nice.
Display a count of updated threads (and notifications) in the GOG favicon (and page title) and reload hourly so a browser tab can be used as an update notifier
You may also like Popup Blocker Script.
Since GOG.com doesn't offer any kind of e-mail notification for forum updates, this extension allows you leave your favourite threads list open in a tab and use it as an update monitor.
This has three benefits:
UPDATE: As of version 6, GOG notifications (eg. library updates, chat messages, friend requests) will also be included in the count.
As these are known for not updating immediately, an "Ignore Stuck Notification Count" command is provided under the Greasemonkey "User Script Commands" submenu, which operates as follows: