Rated 3 out of 5 stars

If you are having getting Ctrl-Tab to work on firefox4, I fixed it by changing the following configuration to true in the about:config page:
browser.ctrlTab.previews -> true

Essential Addon Rated 5 out of 5 stars

Very essential extension. It helps me traverse the tabs by the most recent one which is a better order for me. If I wanted to select a really old tab I would just select it with the mouse anyway.
And it is very helpful to switch between two tabs indefinitely sometimes.
Does not work in FF4 + Ubuntu 10.04