I have had nothing but hospitality and respect when sitting amongst Dragons fans and Bulldogs fans, with no one around me that I know except my Sharks jersey wearing partner. The Parramatta fans have also been excellent. I have sometimes been embarassed by a Sharks fan around me, so I guess it very much depends on the good or bad luck of sitting near the 99% of all fans who are decent or the 1% of all fans of all clubs who are tools.
Personally, my least enjoyable experiences have been from Roosters fans, when I have been to the SFS (or whatever it was called at the time) with a Roosters mate of mine, but since I have been there a lot more the sample size is so much larger, so there is a higher chance that one or two incidents will stick in my mind.
I also went to a Tigers/Penrith game in my Sharks gear, and a fight broke out between a Tigers fan and a Penrith fan who looked like they crawled out of the setting for 'Deliverence', and trod on my partner, as well as some little kids sitting near by, in their eagerness to show who was the bigger idiot. But all the other Togers and Penrith fans were very annoyed with these two also.
My best experience was in Auckland, but being in another country with an obviously Aussie accent just provided a lot of scope for pleasant conversations, so maybe they are no nicer in Auckland than elsewhere.
