> The thing with extensions like Tree Style Tabs and Sidebery is that nice as they may be, they’re awkwardly bolted onto the browser’s UI and the best you as a user can do to try to fix that is to hack on your userchrome and then pray that your hacks won’t be broken in some upcoming browser update.

Now that firefox has native vertical tabs it's possible that the the integration can get better in the nearer future since I doubt the vertical tabs feature (which i haven't used yet) has tabs on the top AND side.