For me specifically, it's not if she's nerfed or not. It's how playable she is. For example, my second character in Melee is Bowser (yes Peach, then Bowser. I'm weird). He was tough to use, but at least he could at least do some stuff: kind of combo, wonderful power, amazing edge-guard game. Many of Peach's current moves look kinda useless.
Smashes:
Foward and Up smash are good. I guess they should be used as kill moves. Down smash is useless. From what I hear, I probably just won't use it in matches. It's gonna be tough to go from a "D-smash to your heart's content" mindset to a "Stay away from D-smash at all costs" mindset.
Tilts:
I hear ftilt is better. Utilt has more range, but apparently it's still situational, since if the person is next to you it won't hit them
jab:
too much knockback to combo, not enough to kill or anything
Specials:
up-b is slow. turnips are weaker and disappear. side b got slight buffs, but still seems like a situational move. Toad got some buffs, but counter moves get too predictable if used often.
throws:
No combos, not enough good knockback
It seems like they majorly nerfed all of her good melee attacks, and buffed some of the average ones, but not enough that they make up for her nerfs.
The thing is, that's all just what I've heard and seen. I have yet to experience Brawl for myself. However, if all of this is true, Peach seems to have been nerfed to death, and I will most likely switch.