The Smash demo (with playable Mario, Link, Pikachu, Megaman, and Villager) released in Japan... well, I don't actually know when, but I noticed it today when I was in the eShop so I grabbed it. I have some opinions on the controls. (And note, I write this as a very casual Smash player.)
Maaaan the 3DS controls are so uncomfortable. :( I don't know what 3DS LLs are like--hopefully they have a better design on the circle pad than the original 3DS--but playing the game was a bit of a hassle. A slower character like Link was alright, but trying to control Pikachu with the circle pad was SUCH a pain. I sort of got used to the circle pad--or at least started training myself to deal with it--by the time I put it down for the night, but I never really got the hang of hitting L for throwing items. It's really awkward to throw in a particular direction when you're controlling the direction with the same hand. Settings aren't unlocked in the demo, though, so fingers crossed that you can map buttons in this game, maybe.
The game looks a lot better than I expected, though. It was a little bit difficult to tell my character apart from others when we were playing the same character, at times, even with palette swaps, but that might just be me sucking at the game. I noticed it was a little hard to follow the action when everything zoomed out but, again, I might just suck. I feel like I could also attribute both of these to playing on the original 3DS with its smaller screen. I don't think this game was made for my 3DS. But the graphics are good, especially for 3DS. I admittedly didn't think I'd like the hard black outline on the characters but it looks fine and it's definitely needed to help separate the characters from the background.
I have to say, I'm kind of disappointed. When this was announced for 3DS my very first thought was "ugh, I bet it won't control very well" but I figured... hey... they wouldn't go to the trouble of developing it for 3DS if they weren't confident in the controls, right? The issues I'm having are exactly what I expected. The button layout is awkward and unintuitive to me. (I've never played Smash with so few buttons before--I guess if anyone played Brawl with the Wii remote this might feel cushy.) Hopefully it's better on the 3DS LL but I have no idea what those even feel like so all I can judge is my old 3DS model. I'm gonna play a little more here and there for a few more days to see if I can get better and get over the awkward controls but I have a feeling I won't, so I'm probably skipping the 3DS release and just getting the Wii U version when it comes out.
Aside from the physical controls, I did like the gameplay, the speed, and so on... so I'm excited to play the Wii U version! Whenever it actually releases, anyway.