I do use Opera, It is an excellent browser and these are the reasons why I chose it:
Opera in my tests is faster than FF4 (by a long shot) And is at the same amount of speed as chrome. (the difference is in fractions of a millisecond)
It has all the features built in which would require FF or chrome to have extensions.
It has turbo, which speeds up the connection if you are on dial-up.
Private Tab browsing so you don't even have to open up a new window.
Opera Mail, with simple UI and excellent mail management.
Opera Unite with great server capabilities.
Customization. (you can literally customize EVERYTHING on this browser)
The whole User Interface, including all the menus, keyboard commands, mouse gestures, toolbars, and even individual buttons are extensively and easily customizable, using a user-friendly GUI driven interface for most features . Every possible function the program can perform has an internal command that can be easily used.
Widgets.
Smooth and minimalistic UI.
Mouse Gestures. (Navigating in other browsers feels slow now...)
Web Panels. (Useful as hell once you start using them )
Content blocker. (cant stress this enough, it is epic!)
Built in IRC.
Opera Voice. (for navigation text to speech etc)
SESSIONS
Another opera innovation, it allows users to save entire collections of open pages, along with their browsing histories (back and forward buttons) and settings so that they can be opened later. These sessions allow you to easily switch between projects you may be working on or otherwise different sets of pages you may use. You may also choose to start Opera each time with certain sessions (like a home page, but multiple pages, possibly daily news, etc). Or you can have it automatically save and restore sessions such that if you ever have to close Opera, you can reopen it later and pick up right where you left off.
SECURITY
Opera has a very good reputation in the security community for always fixing any possible security issues as soon as possible. It was designed to be secure from the outset, and does not support the sorts of dangerous technology so heavily abused by trojans and worms and hijackers on the internet.
NOTES
Simple but brilliant - select any text on a web page and simply copy to a note (using a context menu, a keyboard command, or defined mouse gesture) - it gets saved in a co-tree view tree view structure (folder-ed hierarchies to fully ORGANISER your notes) - It is fully search-able too (progressively finds matches as you type the search pattern). You can double click the note to go straight back to the original URL the text excerpt was from, or you can quickly mail it to a friend! Great for web research when you find small snippets of info; how many times have you read some paragraph, then later wanted to find it to quote it but not remember the source’s address - this is the fastest (only) way back to the page. The Firefox extension, Quick Notes , and Maxthon’s ‘collector’, are very weak in comparison (only use tabs with no organization of research notes possible); and IE or other browsers simply don’t have this great feature
BOOKMARK FUNCTIONS
Great bookmarks implementation - uses both nicknames AND keywords/descriptions to provide lots of additional information for stored bookmarks. Nicknames allows the bookmark to be easily retrieved in the address bar; if you give hotmail.com the nickname ‘hm’, then simply typing hm takes you to hotmail.
There is also a great dynamic quick search function in the sidebar and bookmark manager that progressively updates to show only bookmarks matching the search-term (if you use keywords, you’ll get a dynamic view of related bookmarks that may not even be in the same folder!). Firefox, in comparison, cannot search anything but the titles of bookmarks, losing most of the power of bookmark keywords and descriptions.
SPATIAL NAVIGATION
For those Keyboard surfers, this is a really killer feature, allowing one to navigate links in a page depending on their spatial (and not document) location without needing to use the mouse. Again, a totally unique innovation of Opera.
You can create new search fields. ie just right click a search box, and click create search. Now you can search that website no matter which website you are on.
Toggle graphics on and off. This feature lets you enable and disable graphics, if you are suffering from low bandwidth, you can even ask it to pull images from the cache.
It has all these features, and is still as fast as the fastest around.
You can download Opera here: http://my.opera.com/community/download.pl?ref=abdur92&p=opera_desktop
Hope I helped. :)