Ok I'll post my peach write up here and the social thread.
I have really good experience against Peach. From what I see from ILLMATIC if you're playing on somewhere like FD where there aren't platforms, all they do is float, space, and dair if you get underneath them. You have to basically run in and fullhop a nair, fastfall, and run away. If they airdodge, then do NOT fastfall or dair or whatever. They can utilt, uair, what ever. They own when you're in the air. If they pull a turnip semi-close, run in with shield to pressure and/or grab. Almost ALL of my grabs I get are when they pull turnips at the wrong time.
Smashville is very different. Same with the dair, but they can jump on the moving platform and spam turnips. Do not try to jump offstage and upair them while the platform is off the stage. They can bair you SUPER easily.
As for bans, ban either RC or Brinstar depending on the player. Illmatic, I know, loves RC against me, and he loves Brinstar against basically every character minus MK.
On Brinstar, just always be watching out for peach bombers because they can bounce off the breakable pieces and they can float off of the recoil. Stay away from them when the lava is rising, or you can pressure them with squall (if you find an opening).
On Rainbow Cruise, the first section is sorta iffy. Often Illmatic just waits on the right side and throws turnips. Just stay against that wall upair'ing/uptilt'ing and wait because if you jump then they will just jump up and dair you (and you can't do much cause you're in the air.) The second section, work really hard to staying beneath her at all times. You have a great vertical recovery so it doesn't matter if you're really low as it rises. On the pendulum thing, be pretty careful. We're both not very good here because we just suck on RC, and the tilted platform can often mess her up with her floats. Get to the next part asap. Next part is a weird BF, just play it as it is.
For CPs, do what you feel comfortable on. I like FD, BF, and YI, but I've heard that Lylat is good because of the tilt of the stage (messes up the float).
For general tricks, remember Peach can fair onto the ledge, gimp and keep Nana separated easily. If she tries to sideB (Peach bomber) to the ledge too high, dtilt which can gimp her well if she doesn't have a float.
Her fair is safe if spaced well. If they jab afterwards a well-spaced fair, roll or run away (you don't have any options). If it's misspaced, you can grab. Squall is very odd because if they DI right they can nair (which ALWAYS beats squall). I find squall useful when you're at midrange when she's pulling a turnip because she can't nair or dair. All she can do is throw her turnip (squall beats turnip if it hits the hammer (so don't squall above her)). Grounded squall is a very good mix-up, I use it a lot more often.
This is an weird idea that I've taken from Japanese ICs but I've tried fitting in some FH/double jump fairs if they float really high. It often works because why would they fair when they're floating high??
For basic basic strategies, running up to her in shield has lots of options. If they have a turnip, they will either jump, glide toss forward or back. If they jump, space a nair. Glide toss back or forward, nair/autocatch the turnip and throw it back. Often if they GC forward, the nair will hit them (you really gotta predict when they throw or else you'll fail). If they don't have a turnip, nair or turn around and bair because well spaced/timed things can beat a LOT of things.
If you're stuck in your shield in her dair, ROLL AWAY. Another option, risky though, is a buffered nair oos. If you time it differently, you can have Nana only nair while you run away (super safe as long as Peach doesn't nair because hers is faster (the reason she doesn't always nair after dair is because often she's daired several times and she's running out of float and falling nair isn't good against our shield)). ONE OTHER OPTION (but very situational) is jumping oos and buffering an up-b. It beats dair hits, but they can completely avoid it if they move after their dair.
In the past, Illmatic and I went to timer/close often, but lately we've evolved the matchup and it's really not based on the timer.
Illmatic, please comment!