Double post but... I got to play 2.5 yesterday!
I played part of the Halloween Town demo as well as the BBS Aqua demo and a tiny bit of the Ventus demo (last person left it on the Ventus demo and I played it for like a half minute before I did a soft reset). KH2FM looked gorgeous, just wow. I can safely say this looked better than anything that came from 1.5. KH2 of course was a better looking game than KH1 or Re:CoM were on PS2, so most of the detail comes from that fact, but it being rendered in HD really emphasized how much detail there really was. Other than that, it seems to be the same great game and it'll be awesome to play it on PS3.
Now Birth By Sleep though... it looks better than it did on PSP, for sure. But it wasn't really comparable to KH2 or anything in 1.5. For some reason, fish faces in this game stood out a lot more than they did in 1.5. Every single time I saw young Kairi I kinda cringed. Aside from that though, Ventus and Aqua (and probably Terra, tho I didn't see) had great model improvements. Mickey seemed to still have his BBS model, which I thought was kinda odd since I thought they'd swap in the 3D model or even the model they're using for Re:Coded. I hope that at least MX and Vanitas will receive updated models. While graphical improvements of BBS didn't really excite too much, playing with a DS3 controller instead of a PSP was great. The camera felt greatly improved and didn't have the problems 1.5 did when they added the 2nd analog support. All the loading issues BBS had seemed to be all gone, and the framerate seemed to be locked at, what I presumed to be, a steady 30 FPS making gameplay feel a lot more smooth than the PSP version. 30 FPS isn't great but is more than playable, just seeing no drops in the framerate was awesome.
So yeah, overall, 2.5 is looking pretty great and I can't wait until December to get my hands on it and for the rest of you to see it too!