The interface, like many WebUI extensions, is pretty horrible. Notifications are extremely slow and take a long time to disappear. It’s almost impossible to move tabs from one group to another with accidentally loading the group. Similarly the group list has two sides: the left side will load the group; the right side will load a tab list of the group. This is not very clear as this behaviour isn’t normal for a drop-down menu.

Loading a group with a large number of tabs (despite the option to only load active tabs) will try to load ALL TABS, potentially freezing your computer. Firefox itself does not do this when loading tabs, so it’s a mystery why this extension does.

Finally the Manage Groups page shows nothing, so no managing is possible.