Opera has extensions just like firefox and chrome. there is a button in the menu to add extensions or click here : https://addons.opera.com
the 4 extensions i use are :
adblock - https://addons.opera.com/en/extensions/details/adblockforopera/?display=en
( its the same adblock FF uses )
exchange - https://addons.opera.com/en/extensions/details/exchange/?display=en
( shows the currency on any site as my own, right on webpage , i use this for buying on ebay )
Gmail checker - https://addons.opera.com/en/extensions/details/gmail-checker/?display=en
( it puts a little gmail icon on search bar and shows message count )
Fbook notifications - https://addons.opera.com/en/extensions/details/facebook-notifications/?display=en
( same as the gmail above ).
I also downloaded a nice Black skin that goes with the gnome desktop im using. https://addons.opera.com/en/themes/details/o_12/
the REALLY nice thing about opera is the speed dial, if you open new page you will see the big blocks in the page, you can add all your favorite sites there and it will show them with previews. now when you want to go to a site you simply click on a speed dial and walla... its also nice when you busy on a web page, you just click new tab and see dials right there and click on desired one. quick and easy...
You can also customise opera alot, go to "opera/apearance/toolbars" and set progress bar to pop up at bottom. you can tick "show hidden toolbars" and drag and drop the toolbars as you want the layout to be, set placements and so forth. Opera is FAR more customisable then any of the other browsers ( in both FF and chrome you can download preset customisations, in opera you can drag and drop and change it how YOU want it to be ). the speed is also much faster and you can add alot of the same extensions as the other browsers.
Im sorry, but after i moved over to Opera it was like heaven... Ill never go back to FF or chrome ever again.