Very much follows the spirit of "Tab Groups" from the old FireFox.

However, a list of critiques:

- Support for FireFox Sync is almost mandatory for next update priority. The lack of being able to sync my container definitions between all my PCs is going to be deal-breaking if it's not addressed.
- Tab Right-Click assignment of container group.
- Wider range of colors and icons would be nice.
- A better customization experience for power users to control how sites and tabs are categorized, and the edit process for container definitions.

You're on the right track. Please listen to the feedback!