The Firefox Menu :
Looks like new File Menu of Office 2010 which opens up the backstage of Office Application got into Firefox. They are same except that there is no drop-down menu which shows up in Office 2010.
Chrome Like Tabs
Chrome made the tabs go on top and are more curved on the corners. The same features are in FireFox 4 now except that they look gentlemen. 😉
The style of IE Menu
The way menu opens in IE which is similar to how right-click opens up in Windows Explorer is not in Firefox 4 Bookmarks.
IE 8 Like Multiple Instances :
Now like IE 8, Firefox4 also displays a stacked icon on the taskbar which means one for each tab you open.
The Opera Speed Dial :
Opera has Speed Dial feature where you get to see preview of each open tab. Firefox 4 doesn’t have speed dial exactly but similar feature which lets you see the preview of open tab and its much advanced than what Opera has.
Its more for organizing tabs and grouping which is one the best features of Firefox 4.
Did you spot any more features ?