I recently downloaded Opera and have had no problems with it yet. Firefox is my defalt browser. i havent upgraded my IE in forever so i do'nt know what's going on with it. yeah firefox is a plus with all of the plugins and themes. i'm still getting used to Opera though. i basically like any browser that has tabbed browsing and isnt IE. i don't get any pop ups at all with Opera.
I personally use Firefox, I orignally used Opera, the main reason for my switch was my old computer took awhile to load Opera for some reason whereas Firefox was that tad bit quicker