I watched some streamed footage of G&W yesterday; here's what I noticed as a G&W main in Brawl:
-By and large, G&W seems to have seen some buffs and some nerfs, quite possibly net positive. He seems all around faster (especially grounded mobility), but his attacks also seem less persistent (lingering hitboxes was G&W's big specialty in Brawl, and I kinda felt like most of his stuff just lingered less in smash 4).
-Jab finisher has an awkward looking animation, seems relatively inferior to others (still a big improvement on his useless rapid jab).
-Utilt is way, way faster now.
-Ftilt and dtilt seem about the same, but dtilt seems to persist for a little less long (maybe?).
-Usmash may linger less but is otherwise very similar looking.
-Fsmash has a new and horrible animation. Less range, way less persistant hitbox, still looks really unsafe on block.
-Dsmash has... substantially more range!!! I wasn't able to see hit properties or get a good sense of its speed; it maybe is a little slower, but the animation is different enough with the bigger hammers that it could easily be an optical illusion.
-New dash attack, hilarious looking but also looks worse than the Brawl one.
-Chef seems to generate food at a wider array of possible angles, otherwise seems the same.
-Judgment Hammer is still really bad, slow, no range.
-Fire is like in Brawl except it falls way slower with the chute out. Thank you for random buffs to G&W's best moves?
-Oil Panic seems a little less punishable on whiff (pulling out bucket, not getting anything). Hard to say. Was used on the ground, cannot comment on momentum properties.
-Nair has the exact same animation as Brawl, great news for G&W for sure. I can't tell if it juggles as well; the player never got a clean hit.
-Fair has the same naimation as Brawl as well, can't tell if it hits as hard as before. It may be a bit less persistent, hard to say.
-Turtle, the greatest move, was back in full glory. I couldn't confirm the landing hitbox; everything else looked identical down to the animation.
-Uair still has the wind, still hits with at least some force absurdly far from G&W. Hit nearly the entire vertical distance of FD on Master Hand (could tell because his % meter flashed).
-Dair is still plunging. I wasn't able to confirm if he could still air control during it unlike every other character with a plunging dair.
-Uthrow is the same as ever, fthrow seems to throw at a lower angle (either that or this player was using worst DI, DIing down to die earlier to the fthrow, can't be sure on that one). Bthrow and dthrow weren't used. Pummel still looks really slow but maybe a bit less slow than Brawl.
-G&W's utaunt and side taunt are the same as Brawl. His "flipping people off" taunt has been replaced with a "napping on the ground" taunt that is pretty funny itself.
-G&W's shield actually covers his whole body, unlike Melee but like Brawl. Just thought I'd confirm that point.
I really wish I was able to be more sure about stuff; G&W was looking pretty good in that footage, mostly being used by the AI and preventing himself from being unlocked. Unfortunately, until a skilled G&W main actually gets their hands on him, it's really hard to be sure about stuff or give truly good technical details about how he operates. I do plan to branch out beyond "G&W only" in smash 4, but if he's good, I'll definitely always maintain a pocket G&W so I'm still really interested in how he turns out!
Since you did this, I'll give my input:
-Less lingering may not matter depending on other buffs.
-Love ftilt's animation. May be more powerful (close to PM level? *fingers crossed*).
-I actually like fsmash's animation. The range does look mega nerfed, maybe back to Melee range.
-I was like "dude!!!!" when I first saw new dsmash. Maybe the sweetspot will be bigger too (although Brawl sourspot is lovely).
-Dash attack looks like it might be pretty strong, although it's hard to tell in Classic mode. May even kill at high percents. If it still stage spikes, it'll be better than Brawl due to the new ledge mechanics.
-Chef appears to have low endlag. It may finally be a decent option in neutral.
-I didn't see any Judgments hit but hopefully the numbers other than 6 and 9 got buffed. If it's anywhere close to PM in general effectiveness, it may finally be worth using. If not, hopefully we get some good customs for Judgment and Bucket.
-None of the streamers used Fire much. If it really does fall slower, hopefully it still drifts as fast as in Brawl. I hope it still kills off the side, and it would be nice if you could attack out of it a little bit sooner.
-I'm hoping for some usable custom Buckets. Without hitstun cancelling it's almost useless in most matchups, even if it still momentum cancels.
-At first I thought fair had less landing lag, but I'm not sure. Either way, still bad on shield.
-Lack of SDI will make bair as amazing as it was in Brawl's early days. Hopefully it still has the hitlag so it looks good to land. It's not nearly as satisfying in Melee and PM.
-Uair looked pretty strong. It may have some legit kill potential. But once again, Classic mode.
-I'm not sure if it was uthrow or dthrow, but one of his throws looked a lot like Melee dthrow. Even at high percents, it hardly sent the opponent anywhere at all. May have set knockback. Imagine if it comboed into up smash.
-G&W's shield seemed to break more easily than other characters against Master Hand, but maybe he just got hit more.
-I love the new light blue color. The sky blue in Brawl was an eyesore. I didn't see any other new colors, but I'm hoping for white.
-G&W should have good combo potential off nair, bair, uair, utilt, throws, and maybe up B.
-Call me crazy, but G&W looked heavier (Classic mode disclaimer). He may actually be able to take a hit in this game.