This is a great extension, it reminds me a lot of Trello, very nice UI and so far has been very stable.

There are a few things I'd like to see improved:

1. Needs a feature to export / import tab tiles for safe keeping / backup.
2. Would be useful to have an option that would highlight duplicate tabs, it's easier than ever to have the same tab open in several groups, so having this feature would be pretty useful.