Opera 10.6 which was released yesterday is currently one of the fastest browsers. It has beaten Chrome in javascript speed test. It also features better support for HTML5, WebM video support.
You can now install it on Ubuntu via PPA.
Add the PPA in your repository:
sudo sh -c 'echo "deb http://deb.opera.com/opera/ stable non-free" >> /etc/apt/sources.list.d/opera.list'
Add the key:
sudo sh -c 'wget -O - http://deb.opera.com/archive.key | apt-key add -'
Update your package list:
sudo apt-get update
Finally install opera:
sudo apt-get install opera
Enjoy the all new opera!
Cheers!