Technically speaking, it's gorgeous. One thing Square has always been able to do is put lots of pretty pixels all in a row, and this game is no exception. Gameplay is just as clean. I had some initial fumbles due to my brain's training on the Playstation controllers from my playthroughs there, and there are things I'm still not certain aren't better done that way. But it all works properly.
That said, it's not without a price. Starting with an 18.7 gig download, and some serious system requirements. I'm not sure how close to the knees you'd have to hack the graphics settings down to run it on a marginal machine. The default worked well for me, but this machine has a fair amount of muscle.
It's got far more in it than I expected. It's not just an area or two. It includes all of Chapter 1, with a certain amount of the quests and hunts available. They're not all there, but the ones that are there are complete. The story included is rushed, of course, because so much had to be elided. But hey, all the "Entourage Simulator" parts were up and running. I got to fish, and Gladio got to setup the tent and camp, Ignis came up with several recipes and Prompto took a couple real winner pics. The end is a montage of the next several chapter cut scenes, but it doesn't give away too much.
Does it work as a demo? Well, it's made me want to go play the full game again, but they had me with the Playstation version. I can say if you're on the fence about it and prefer to play PC games, you could definitely do worse than invest the time in that demo download and see for yourself what you think.