What can Opera do that Firefox Cant
Save Sessions
Split Screen view
Mail Client
IRC chat client
Voice Navigation
Voice Reading
Download Manager
Bittorrent Support
Small Screen Emulator
Hundreds of Widgets
Thumbnails on tabs
The ability to move elements like tabs and menus anywhere you want, top, bottom, left, float, etc
Retrieve closed pages from history trash
Etc
http://www.opera.com/products/desktop/Opera has more features than any other browser and they have been doing this for a lot longer than Firefox.
Firefox just has better marketing and a cooler logo/brand image.
