I have two suggestions for the tab handling:
- Tabs can be closed with the middle mouse button, like in any modern browser, great. But it works on mouse-button-down, and to be consistent with many other controls (window-handlers, ok- & cancel-buttons etc.), it should trigger on mouse-button-up, this can help to prevent accidental clicks (you can drag away from your clickpoint to cancel the action).
- Favorites can be opened in the current tab, it would be great if you could press the entry with the middle-mouse button to open it in a new tab (also standard browser-handling).
These improvements are pretty small, but as a user working with it I have to say these are great details.