a couple of notes for anyone that cares:
tried Bowser at the sm4sh demo, the mechanics seem to help and hurt Bowser at the same time.
His up-B OoS is still around, which most likely means that it's still good
Bowser's Klaw is a bit more "under-handed" now. what I mean by this, is that he seems to grab from below more and even in the air. I'm unsure of its range though, and Klaw Hopping seems to be removed...at least, it's not in this build.
His firebreath looks a bit odd, and his down-b is ridiculous as you probably saw in the invitational
the only colors that returned so far are Bowser's original costume, and the black shell with red hair. there are two new costumes: there's one that resembles his red-team color, although it looks pretty different too, and there's one where his skin is green (it's not the blue shell palette, I've no idea what the **** it is honestly lol)
his jab is still good, but his ftilt looks a bit more animated and seems to be slightly shorter, but pulls out and back faster. bowser in general is more animated this time around. His air mobility is still solid, but I personally think that everyone in this game looks stupid when they jump now due to the "side-profiles being the same in both directions" thing sakurai revealed a few weeks ago.
his upb in the air recovers faster from lag as well. His speed is an obvious improvement, but his aerials have seemed to change quite a bit too on how they hit. the only ones that remain true more or less are U, F, and DAir and even those have been tweaked. His backair is a kick with both of his legs, as you all probably know.
I was unable to test whether grab releases are still a thing or not, but given how sm4sh seems to operate, I really feel like I can't judge Bowser yet. parts of the game still look and seem awkward.
mechanics wise, smash 4 seems to be fluid like Brawl, with hitstun being in between Brawl and Melee. It seems like the more damage you have, the less freedom you have over (s)di and things like that.
fast falling is ridiculously fast in this game
and a reminder that obviously this isn't the final build of the game. the character select screen only had characters up to greninja's reveal, and i'm sure he'll probably be changing a few other things