Demo's out now for everyone. Just downloading it. I'll come back with my findings.
Updating with my thoughts:
Okay, I haven't played SSB since the N64 days so I don't know how much has changed since then. 3DS version handles just like it though. Really fun game.
Couple of things I don't like. Jump is X and not B. Very confusing.
Secondly, I get the feeling that this game wasn't made with the original 3DS in mind. The screen is just too small so it can be hard to see what you're doing among the chaos. I think it would be better on the XL.
Overall, a pretty decent game though. I wish Nintendo would do a cross buy promo like Sony does, so you could get both versions.
X and Y for jump is how it was on the Gamecube (and apparently how it mapped to the classic controller on the Wii). I thought I might would prefer A and X to be the jump buttons, but it would make jumping and doing one of the moves more awkward, since it'd be easier to press Y and then B or X and then A so I think it makes sense.
Thanks for the feedback, although I kinda want input on how it compares to Melee and Brawl. The Wii U version I believe was going to target Melee's feel. Not sure about the 3DS version. I liked the first game and Melee. Brawl just was lackluster all around to me personally.
I don't have a 3DS yet, but this might would be the game to finally do it (and since I could possibly talk some friends into getting it).
Oh of course they don't, because then they couldn't get sales for both. Apparently they are going to allow you to share characters (I'm assuming stats?) between the two versions, and even use a 3DS as a controller on the Wii U.
I haven't actually been paying too much attention, so I'll have to look at what they're all doing. Will either version have a stage creator like Brawl? If so I hope it's a lot better than it was in that, and/or it has better stages than Brawl. I didn't really enjoy many of them, so ended up playing mostly on the previous Smash Bros stages.