What I found out, keep in mind that I probably missed a lot of changes :
Stuff that looks untouched :
-Rolls (:/)
-Shields
-Spiking with trapping hitboxes such as Ness/Falco's Fair, Greninja/Sheik's Uair still seems possible
-Sonic, Pit, Dark Pit, Jigglypuff, Charizard, Donkey Dong, Peach, Palutena, Yoshi (will edit later)
Bugs :
-Bomb canceling fixed
-Turnip canceling fixed
-Yoshi teleport fixed
-Wectoring fixed
-Greninja's Dair cancel fixed
-Hyper Rollout fixed
-Villager's rocket kill on the ledge fixed
Bowser :
-Bowsercide = Bowser dies first
-Fsmash deals 2% less damages, meaning that Dedede/Ganondorf now have the most powerful Smash in the game.
-Down tilt's second hit is harder to connect
Rosalina :
-Luma timer increased to 13 seconds
-Nair deals less damage, less kb as well
-Neutral B's distance covered has been lowered (Which is, in fact, a buff, that shit was hard to land properly.)
-Luma comes back faster
Ness :
-Down Throw nerfed from 9% to 7% (;_;)
-It now does the correct amount of damages on G&W
Marth :
-Looks like his Dthrow/Fthrow give more followups. (fuck yes)
Lucina :
-Looks like her Dthrow/Fthrow g-oh wait I just said that two lines ago
Ike :
-Ike's Fair is significantly faster
-Looks like it can autocancel as well
-His Nair comes a bit quicker
-Jab looks fixed so all 3 attacks connect properly
-Ending lag on his Ftilt and Dtilt reduced
-Back air seems faster but I'm not sure at all
-Back air's damages increased by 1%
Toon Link:
-Jab damages increased by 1%
-His Utilt still does 5% despite the fact it does 6 on Wii U
Shulk :
All Shulk's moves but Backslash are buffed, most of them do more damages (Ranging from 1% to 3%)
Little Mac :
-Jab does less damages
-KO Punch got buffed, KOes earlier (Somebody on Smashboards calced : It used to ko Jigs at 19% with vectoring, now it kills at 13%)
Falco :
-Blaster comes out quicker
-Our prayers got answered ! Dair is faster. (Not instant but still quite fast now.)
Sheik :
-Looks like needles now have some ending lag to em
-Down B has less knockback
-Uair has less knockback
-Fair deals less damages
Zero Suit Samus :
-Side B now connects properly
-Air Dodge's landing lag standardized to the usual 22 frames
-Neutral B has more ending lag
-Neutral B quick shot has less range
Greninja :
-Uair nerfed. Harder to land all the hits, less knockback.
-Can't fastfall during Shadow Sneak to reappear lower anymore.
-More lag on Usmash
Olimar :
-Pikmin Toss does more damages
Pacman :
-Hydrant got sturdier to the point Pacman's back-air can't send it flying
King Dedede :
-Down Throw now sends upward
-Dededecide kills Dedede first now
Zelda :
-Up tilt does 1% more damage
-Looks like Din's Fire has less ending lag to it
Ganondorf :
-Looks like Nair has less lag
Megaman :
-Looks like Leaf Shield throws out faster
Meta Knight :
-Nair deals more damages
-Down B sends more horizontally, allowing for earlier KOs
-Fthrow damages fixed
-Bthrow has a tiny bit more knockback
-Rejoice ! Bair KOs about ~25% earlier ! MK has a ko move eveybody !
Kirby :
-Foot based attacks have a bigger hitbox, kind of like Yoshi's tail attacks.
-Kirbycide kills Kirby first
-Looks like he's faster
-Nair has more lag ?
-Uair faster
-Upsmash has a sourspot
Luigi :
-Fsmash deals more damages
Mario :
-Utilt deals less damages
-Looks like he's heavier
Dr Mario :
-Looks like he's heavier as well
Wii Fit Trainer :
-Looks like Nair deals less damages, need confirmation on that one
-Air Dodge's landing lag standardized to the usual 22 frames
-Uair deals more damages
Pikachu :
-More knockback on Fsmash, Side B and Down B
-Thunder's hitbox no longer is divided in 4 separates ones
Wario :
-No longer has that troublesome release animation so some characters can't combo him as easily as before
Link :
-Fsmash's second hit connects more easily
Bowser Jr. :
-Dthrow deals less damage
-Dair deals less damage
R.O.B :
-Up B's fuel comes back quicker
Sources : Me, Smashboards as well, Neogaf.