Ok, I've written this up already.
I'm sure one will say that they can make FF do all Opera can do with Add-ons, but here goes.
1. Mouse Gestures (can't browse without this)
2. Mail (all my accounts are set up to auto check every 5 minutes)
3. Right click: Speech, dictionary, go to web address, multiple searches, translate
4. Notes
5. Personalised settings for different webpages
6. Speed Dial
7. Ctrl+Z to open closed tabs
8. Reload every (reloads pages every how many minutes)
9. Opera link. (Carry my bookmarks, speed dial, and notes to any computer, anywhere)
10. Quick search. (for example in the address bar to search all I have to do is type w):
Off the top of my head, that's why I use Opera over all others.