I'll give updates from the E3 Build (which i played at PAX last week). These are obviously not the most recent build of the game, but I'll give updates for those curious in case a lot of these were the same
-ZSS seemed the best.
-SH aerials autocancel, and she has low landing lag in general
-Safe range
-Down throw combos to Uair or Fair which is amazing
-Uair combos to basically anything
-Bair is pretty strong
-Jumps and double jumps very high/very fast
-you can Air dodge into a Zair and have no landing lag (but the majority of characters, who do not have a Zair, have to suffer ~20? frames landing lag, making characters that can Zair really good since you can do it even the frame before you land if you want and be fine), down B is REALLY good evasively.
-Down B is really good evasively as it's hard to catch her. You can be shielding, then jump and down B and escape to a new position quickly. It's useful in almost any situation to get to a new position fast and safely.
-Up B OOS (out of shield) is very good if they are hitting your shield at close range and I got KOs at 90 with it.
-Bowser is good due to weight + power.
-never loses FFAs
-SH Fair/SH Bair both Autocancel. But you cannot double jump out of it
-Forward smash and Bair hit REALLY hard
-throws far
-very heavy
-koopa klaw is a very fast grab but not a ton of range
-up B OOS still works and is easy to hit with but does a lot less damage than before also, and you can't fall off platforms with it
-Down B hits twice (a 2nd hit upon landing) and can break shields if both hits hit
-Kirby feels good.
-Bair is good like usual
-Kirby's landing lag is small
-you cannot DI Dair it seems
-Dair combos to other moves
-Up tilts combo into itself easily at low %
-Pikachu's SH Nair and SH Fair both autocancel. Nair landing without autocancel is kind of laggy though.
-Uair does 5% and combos to Nair for 17% combo iirc. Good move.
-Neutral B does 6% and has low lag but low hitstun compared to previous games
-Thunder feels overall faster but less powerful as well
-Up smash to thunder still works
-Pikachu releases from the ledge [grab] faster than other characters by a lot it seems.
-Marth's can SH Fair to a Double Jump Fair before landing. Fair is laggier in the air and has a lot more landing lag, so you may not want to land with it as often as in Melee/Brawl unless you are confident it will hit. A good strategy with marth would be to run at someone then do a rising Fair in place since rising Fairs are still solid damage. You could also in theory just land without an aerial (if they're waiting for landing lag of a fair or landing lag from an air dodge) to mix good players up, since you'll land without lag that way.
-Marth's counter hits a lot harder now
-Mario's aerials have very tiny lag in all possible ways, and quick autocancels
-Mario's down smash is pretty weak
-DK's Cargo to Uair still seemed to work for me
-Sheik has low landing lag
-Sheik is weak and lacks range. I only played Sheik 1 FFA game though since the 3ds line was long.
-Greninja/Wii fit also felt weak but i only played them 1 game each and it was just FFAs
link/toon link/samus/zss can all Zair and have no [noticable] landing lag. The difference with Brawl Zairs is that Brawl landing lag was like 2-4 frames or so always but now if your character doesn't have a Zair the air dodge will just be a third of a second landing lag or so (approx guess. A lot of these are just approx guesses without any true testing).
-Dash Dance shield still works but not as well as it did in Brawl. Felt decent with ZSS/Pikachu at least.
-The first ledge grab has regular invinciblity (but you're stuck on the ledge for a third of a second before you can move it feels like) but the 2nd ledge grab has no invincibility (this may or may not have been changed? idk?)
-DI is in the game, but only like a third? as pronounced as it was before
-Smash DI seems to not be in the game
This is all my updates. It may not all be 100% true but that's the updates I told you guys I would give.
In semi-related news, I'm having 2 websites soon relating to smash 4 (neither are ready yet but will be in upcoming weeks and updated constantly). mew2king.com I will upload anything relating to me at (where I'm streaming, what stream(links to it every day), tournaments, blogs, guides, older archives, etc, random things), and I'm having another site for many other things which I won't name yet. I am hoping everyone will join my upcoming site. If you want these updates, follow my social media (in my signature below). I plan to do a LOT of work for Smash 4 for both myself and the community.