Personally, I think it's fantastic. I haven't played in a large campaign, but hae done it with a small number of players each playing multiple gangs, and we loved it.
I prefer open ended campaigns so we keep going as long as we like, but you can easily set it to a certain number of fights each, or length of time, etc.
When a gang wins a fight, they might get a lot more powerful, sometimes only a little, but in a campaign one or two gangs will get way ahead of the others. It's not a problem though, as there are scenarios to take care of that... or alternatively, you could challenge the tough gang and call the judges on them. This is almost guaranteed to bring them down to a more manageable size.
After a campaign fight, you gain new turf, deal with long term effects of injuries, gain additional traits, collect money from your turfs, etc. There is so much more to the game in a campaign.
Sorry if this is a little rambling... need more coffee
Arabin
