One paragraph in this article made me say "spot on". Emphasis is mine.

Reinstalling Firefox also reminded me of a feature in the forthcoming Firefox 3.1 that I was happy to leave behind: tab-switching behavior. I'm a big fan of keyboard shortcuts, and use Ctrl-Tab hundreds of times daily to switch between browser tabs. I loathe the new Firefox mechanism, which switches to your most recently used tab rather than cycling one tab to the right, and showing a miniature preview version of the Web page instead of actually switching tabs. I don't know if others' brains work differently, but the new mechanism leaves me completely lost in a sea of tabs, forcing me to use the mouse, which slows me down.

I reverted to the earlier tab-switching feature by adjusting Firefox's behavior thus: First, type "about:config" into the address bar, then move past the warning message, then type "ctrlTab" into the "Filter" box, then double-click first on browser.ctrlTab.mostRecentlyUsed and then on browser.ctrlTab.smoothScroll to set them to "false," then restart the browser.

Last time I said it, the reactions were more like "hey your windows box already does it" or "most people like it". People understand it in Windows because WINDOWS are not TABS. They're not organized in a linear horizontal flow so your brain does not try to record tabs' order. And about most people liking the new behaviour, I still don't buy that one, sorry. Not a single person around me, geeks or non-geeks, likes it.