Well... my friend insisted that I use Opera after seeing my blog full of Firefox Extensions. I did just that.. though most of the stuff is heard of and is similar to the extensions... but hey its sleeker and all features like "session manager" CSS viewers and quick note come as a "Standard Fitment" in Opera. They started the Tabbed Browsing concept anyways..
All I'll say is I'm mighty impressed.. Its the most user friendly browsers of them all. The popularity is amazing as Opera became FREE just an year ago. I'm so hooked on to mouse gestures that it seems that I cant use browsers without it. I think opera has also done a "Usability Study" for browsers coz only then would some body take care of small details like a recycle bin for accidentally closed tabs or Email client configuration within browser (the cherry on the cake) and having prefilled values for all popular POP mail services.
These are the things that an everyday user would crave for while using any kind of service or softwares or applications... One does need to get used to the Keyboard Shortcuts.. since u are using different ones in Firefox.. But from features like the "real" mouse gestures (not a fad extension), inbuilt mail client to drag and drop features to Trash Can.. thumbnail view of tabs without opening them... all is great about the browser.
The only thing that I didnt quite like are the Widgets.. they are just so bugging.. opening new windows if I enable them.. they are almost like parallel applications.. so not "opera"like... a real pain in the @&*
Being a Firefox loyalist I miss some of the extensions and maybe I have got used to it.. But I think if Opera incorporate some kinda extensions in Opera.. that would pack a KILLER punch for all of em.... Currently I would call Opera the most user friendly browser..
Just download it and get going