Firefox extensions: Well, they do say imitation is the most sincere form of flattery
Internet Explorer 7's Quick Tabs feature was unveiled back in mid-September last year:
http://www.ie-vista.com/quick_tabs.html
Version 0.1 of Viamatic foXpose was released in November 2005:
https://addons.mozilla.org/extensions/moreinfo.php?id=1457&vid=7825
Now at version 0.3:
https://addons.mozilla.org/extensions/moreinfo.php?id=1457
I think IE7's version is far... neater... less crowded/messy than the Firefox version ;o)