I was in the Curva Nord for Fiorentina-Juve in March 2010 (when Diego scored in like the 2nd minute) and the hatred the Fiorentina ultra's have for us is incredible, an ultra stood just in front of us for the entire game holding up a scarf which was split in half with Fiorentina vs Liverpool on it, and looked at our ultras for the duration of the game, obviously having a dig at us about Heysel, our ultra's were frothing at the mouth's trying to get at him, but the flexiglass was doing it's job.
I love sitting in the curva's, unreal experience.