Nobody has anywhere to go with this unless you do actual testing for an example.
All the stuff I listed I have never seen mentioned, let alone in change logs. I've seen a PMBR state you can use AD through IASA now from Brawl.. but apparently didn't hear Specials couldn't either in Melee and now can. Apparently people don't know this, and it's a bigger game difference than "being able to DACUS now": especially for Marth. And generally I discovered this stuff in-game long before I got answers and realizations.
Let's go over the general list of things that don't exist in Melee but do in PM for just Marth:
SH Fair Special
SH Bair Special
SH Fair WL sooner by 3 frames
SH Bair WL existent (and sooner by 4 frames)
This also applies to just any general air use; now being able to use Special/AD sooner for recovery and such from what is usually around 4 frames or so of IASA on most Aerials before they reach the actual animation end.
What can you do after SH Bair in Melee? ... DJ.. that's it. In PM:
All aerials/specials, except Nair. [Again see the video
https://www.youtube.com/watch?v=IeLklmmYyNk#t=70
And lots of this is hard to do beyond being unknown: even doing something like SH Bair Dair or SH Bair Fair three times in a row I've tested people/you all on and the failure in results is devastating. Let alone being good enough at them to utilize/risk going for in-game; which is why 1 frame of buffer would loosen them to be more usable. Though I haven't ruled out them being not consistently attainable just yet, let alone the rational whether you want them to be. ]
You also can't even b-turnaround Down-bs in Melee: and can in PM (as well as then b-reverse them too). And people don't really know the implications of the physics delay.
NZA are you able to record yourself? Set up DK/Bowser with uncontrolled port, and turn DMG ratio on .5 and see if you can do SH Bair Dair 3 times in a row on him
https://www.youtube.com/watch?v=IeLklmmYyNk#t=258