I was looking forward to this solving my tag organization problem, but ran into two issues:

1. When creating a group, all of the open tabs were automatically added to it. I can't find an option to keep this from happening. It's certainly not the behavior I want -- I want to be able to create groups that I need, and leave all the other tabs alone, and this extension doesn't seem flexible to that extent.

2. Once all the tabs were automatically added to that group, I couldn't remove them without simultaneously deleting all of the tabs. WTF? I ended up having to walk back the entire installation, restore the session and clean up the resulting mess.