Firefox 3.6 has juicy Superbar integration with Windows 7 (and you can disable it)
Aero Peek lets you see what's going on in a particular program without having to actually click anything -- you can just mouse-over it on the alt-tab running-programs menu or on the Superbar. In Firefox 3.5 this works for the Firefox window itself, but not the tabs within. Now, in 3.6 Beta, you can see what's going on in any tab by hovering your mouse over the thumbnail. I do wonder if this requires massive disk-swapping though, or if it takes snapshots -- but I'm pretty sure Aero shows you the window contents in real-time. Either way, it's cool, and beats the hell out of tabbing through 20 different tabs to find what you're looking for.
Those of you that are already using 3.6 might have noticed another neat thing: when you have a bunch of tabs (10+ in our testing) open, you get a "buttonized" list of favicons and page titles, instead of thumbnails. You can still jump straight to a tab or see a preview from the Superbar.
Don't like the Aero Peek integration? You can easily disable it -- if you're worried about the potential performance hit -- just whack about:config into your Firefox address bar and set browser.taskbar.previews.enable to false.
[Download Firefox 3.6 Beta here]