Rated 5 out of 5 stars

Great extension.

- It allows moving among tabs only with the mouse, but unlike Tab Wheel Scroll with a key combination so you probably are not going to switch accidentally.
- It lacks a small options menu unlike other extensions like roTab or Tab Wheel Scroll.
- Needs to be updated for new FF versions (you can change maxversion in install.rdf to make it work with later verions, I'm using it on FF 10.0a1 nightly at this moment).
- Only works with the mouse pointer out of the tab bar, so it also keeps the normal scroll whell behavior on hoovering
- And it's only 2KB

There's also the reversed one: https://addons.mozilla.org/en-US/firefox/addon/tabnavit-reversed/