^(I was just joking about how washed out they look.)
Some observations after watching more videos:
--Apparently a Metroid AT can be insta-killed with Freezie + missile, so that's a nice touch.
--Kirby's flame dash is back YEEEESSSSSSSSSSSS
--Krystal! Probably as an AT, but still.
--Luigi Cyclone & Doc-Tor-nado now produce actual twisters, so that's a nice touch.
--Peach's Toad seems like less of an unwilling flesh shield this time.
--Daisy packs the Blue Toad from NSMB.
--Mushroom Kingdom 2!
--Popo riding the pterodactyl during Iceberg?
--Pichu has Volt Tackle, which is canonical, I guess.
--Ganondorf actually uses the Space World 2000 sword for his smash attacks!
--...Warlock Punch doesn't flinch???
--Some of the Finals actually are still at least partially controllable. Giga Bowser's punches can be aimed, for example. Not sure about Octopus.
--Knuckles appears (as an AT?), chuckle not included.
--Alph hasn't been credited yet, but he's still present as an Olimar alt. Not sure if he'll be indexed as an "echo" fighter, or just a costume change like the Koopalings.
--Greninja used Shadow Sneak! It's super effective!
And remember, "I'm-a Luigi, numver one!"