I haven't played jigglypuff so much (I even don't have brawl yet), but maybe the new brawl air dodge combined with her movility in air can be useful... just like dodge and counter attacks, put yourself behind your opponent, avoid edgeguarding... maybe air dodge -> rest? Is this stuff really viable? It could give Jiggs a chance.
I'm just guessing, really. Sorry if this was already discussed! =/
I'm just guessing, really. Sorry if this was already discussed! =/