Here's a story: my friend's cousin came from Japan to visit his grandma here in Brazil. Guess what? He brought his Wii along with his SSBB!!!
Unfortunatly, I couldn't record anything 'cause I was at my friend's and he hadn't anything I could record with (I know, LAAAAAAAME).
I got to play around three hours with Ness and here is what I felt (I said I FELT, so it doesn't mean everything is accurate):
He felt faster, easier to combo and as light as pikachu. No DJC, only shorthops.
AAA: Same as Melee
F-tilt: Same as Melee, but I did't check if it was able to be aimed up or down.
D-tilt: Same as Melee again...
U-tilt: A little faster, same knockback.
Dashing: A little slower, but more knockback.
F-smash: A little better, since it sends in a more horizontal way, however, no cool sound effects

.
U-smash: A LOT better, more knockback, more damage. I shieldstabbed Bowser and DK with it. Coudn't YYG because the first part had no knockback and was soon followed by the second part.
D-smash: A LOT better, reminds me of N64 version. Fast and powerful.
N-air: Now remember. Didn't use it... But it's Ness' spin.
F-air: Same as Melee, but more useful without DJC. New and more intuitive combos. A LOT USEFUL for coming back to the arena, since its awesome priority.
B-air: Faster, but less knockback.
U-air: Faster, but less knockback, again.
D-air: A LOT FASTER. Killer. Sometimes sends the oponent in a strange diagonal way.
PK Flash: Lower and Faster. That means less combo, more edgeguarding. Very difficult to follow a pop-up into PK Flash. Blue when explodes, less hitbox.
PK Fire: Even better. Comes out faster and traps more (or LV9 CPs are dumber and don't DI)
PSI Magnet: A little less start up and ending lag. The rest is the same. Could absorb Halberd's beam and Spear Pillar's beam.
PK Thunder: A little faster, longer whip. Seemed harder to control or it was the Nunchuk analog. Now Reverse PK Thunders leave almost no vulnerable frames.
PK Thunder 2: Same range as Melee, more knockback. However, if you hit someone or something, you slow down. That's good and bad. Bad for recoveries. Good for launching from the floor and don't end up helpless out of the stage.
PK Starstorm: Awesome in FFAs, but lame on 1v1. Yes, ness IS able to move during its last 3-6 meteors. A good thing is to use PK Flash, since everybody is worried with the meteors and forget about you. My best score was 4 KOs with it in FFA. Each one was KOed once and then my PK Flash threw metaknight on the last meteor.
I tried some combos and none of the ones that relied on DJC worked perfectly. Normal combos such as PK Fire to F-smash worked (DUH!).
Simna's combo is perfectly possible with PKT2 (Didn't try with PK Flash) and it did 56% on Lucas (WTF?!)
Sage's(I think) work well too, but only on really low percentages. (U-air to D-air)
Mine (Yes, I'm claiming it!) worked perfectly. I could KO any character at the start of the battle (OK, he only had Ness, Marth and Luigi unlocked). Here's the deal: Rising F-air, carry down the opponent with F-air, then DJ F-air to D-air out of the arena. I know "It only works if you carry the enemy out of the arena

", but I could almost cross Final Destination carrying Olimar with this combo. Deadly. And I call it SparkingXD
http://www.gamespot.com/video/928518/6185536/videoplayerpop? around 0:32 you can have an idea of SparklingXD (I took the idea from it)
Resuming: Ness is pretty much better, but don't reach N64 Ness. And his new costumes are awesome!!!!!!!!!
PS: Now I'm starting a "Official Ness Combo Thread", all combos proven possible may be posted and the creators will be able to name them. Sage and Simna, I'm waiting for your combo names there.
And I hope all those starting FAQ threads fuse together in the future.
XD