On the plus side:
They make noise & given Sellhurst an atmosphere it lacked
They are organised, create new songs and not scared to try them out
They get in the ground before kickoff & start singing
On the downside:
They are a bit "look at me, look at me"
Some of them don't even watch the game
They have a drum
Songs are a bit repetitive (but I guess most football songs are)
One Palace fan I know hates them with a passion & feels embarrassed by their mock Italian all black get-ups and phoney hardmen routine.
Personally, I think there is a middle ground where you have organised fans who get the singing going, but don't have to adopt foreign football fan styles to do it. I think its sad that barely any songs are heard before kick off these days, apart from away fans possibly. As said a lot before, the way half the Northam wander into the ground 5 mins after kick off doesn't help the atmosphere at SMS.
As far as noise goes, if you have a couple of hundred (mostly male) fans all close together and really shouting loudly in unison, then it can make lot more noise than a few thousand fans who are clapping instead of singing and when they do sing, its only at normal talking volume.