Honestly; although I have yet to play Brawl(I will Saturday, and will only play Jigglypuff), watching what little videos there are, Jigglypuff seems although "nerfed" seems to be on a par with how she was in Melee. I'm not talking as in everything is the same, but I could see her once again falling into the middle of the Tier List.
I believe Jigglypuff's rest seems nerfed now, but that is only because it's new, with the damage after the rest, it may just need to be applied differently (although I am disappointed because I could always rely on rest to help me catch up if I'm down a stock
). Also her Rollout seems to now be useful, as well as a faster startup time, and shorter lag time after the hit/end of rollout. On stages like FD it is a very effective way to stack on Damage on someone who used their jumps at the wrong time, and even possibly kill at the higher percentages.
It's too early to say Jigglypuff has been "nerfed", just as of now, Jigglypuff is new. Like the transfer between 64 and Melee, is going to take some getting used to. I still think BrawlPuff appears to have a relatively decent aerial game. I'll shed more light on this after I actually get to play Brawl
.