I played the SMTV demo at TGS, there's really not much to say about it: System-wise it's pretty much the same as usual, with all the quality of life improvements from recent games. The only things that felt new were the ability to jump and strike enemies for an advantage on the field. There's also a new system to just add a demon's properties on to someone to get their stuff rather than combine them for a new one (this can be used on the main character too) but there wasn't much room to mess with it in the demo.
The graphics felt fine to me and the battles look fantastic but I'm pretty sure that there are going to be a lot of complaints about the graphics on the field (though that would probably come mostly from the console war type people) - Some jaggies are extremely noticeable (particularly stuff like train wires), as are some field objects popping into existence (low draw distance). Of course this might just be a demo thing that they have fixed by the time the full game is out, but if it isn't then I can practically already see the trolling.
I didn't notice any frame rate issues and loading for battles was fast.