I finally managed to get some hands on time with the demo this morning, so feel I can comment on it now.
The state of play was obscenely good, the scope of the game is incredible - and it appears as though they've managed to capture that feeling of a world being beyond the walls of Midgar which players experienced in the 90s, and (hopefully) done the same for the current gen. There could be many things I pick out from the various things shown, but typing the following sentence sums up how crazy this game is potentially going to be.
It has a mini game in which you play football as Red XIII, which basically looks Rocket League. I mean...COME ON! How did this game not take 20 years to develop, and what on earth are they preparing for Part 3? Fingers crossed for Earth Defence Force inspired Weapon battles...
As for the demo, the Nibelheim section is great if you're a fan of the original, not sure what new fans would make of it. It seems it's an old build as the performance mode has some rather crappy textures, as it happens I played on graphical mode and the drop in frames didn't really bother me - and it did look great. What I really loved was seeing Nibelheim realised as a real town, in a similar way to Sector 7 Slums and Wall Market in Remake,
The demo will be updated within the next couple of weeks to include the Junon section, which is more of a large area to traverse and explore, quite different to the more story focused section which is available at the moment. No date for that yet.