I want to bump that. To me one of the most amazing parts of the movies is the general lack of special effects when Gandalf and Sauroman are dueling. Oh sure there's wire work as the two actors (probably their stunt doubles most of the time) are flung hither thither and yon around the room. But no "beams of power" like you see in so many motion picture wizard duels (same thing during the Last Alliance battle when Sauron is kicking butt). Big kudos to Jackson and crew for not resorting to rotscope crap during those times, having the only visible sign being the people getting tossed like nerf balls made it all much more powerful.
All that being said I thought the Balrog looked pretty bad. Though from the discussions I've had I'm alone in that. It happens.