I use IE7 . Love it's interface (yes I know you can get skins for FF..and I do use FF occassionally). Runs faster than FF it seems like for me...haven't used Opera much (but have it installed).
Opera. Can do what Firefox can by default without extensions.
But seriously there isnt a "Best" browser cause they all have their faults.
Firefox is open sournce and prone to more vunerabilties right now.
Opera is closed source and can display some pages wrong. Well techincally not wrong since Opera was the first Windows based browser to pass Acid2 standards.
IE is jsut a mess. Coding for it is horrible. Pages viewed by it can be all wrong. Not to mention the security of it alone is the worst to date.
Chrome is based off a old vunerable version of Webkit. Until they fix that major flaw it will never be good.
So as you see each browser has it up and down points. It is what you choose. We have had hundreds of these polls already. Jsut seach the older topics you will see.