Haven't played the actual game yet, but aside from the visuals and aesthetics in presentation which received a MASSIVE overhaul. It has a completely new soundtrack. None of the old original themes are used AT ALL. Don't have any soundtrack rips (but there IS an OST out), but there are some full videos showcasing the themes
There's a new Esaka!
And a new Psycho Soldier rendition:
The surprising thing is, according to the credits, there's a new team of 4 composers that I don't recognize. Anyone? They're Twofive, Yasafumi Fukuda, Makoto Asai, and Teruo Konishi.
And on a related note, there's been no clear videos showing the music yet, but a video of the credits confirms SNK is in top form doing the XII Soundtrack: Sha-V, Tate-Norio and Usako X (all from the SGZ)