Initial impressions are that this is a straight port-up. Doesn't really look like anything was enhanced along the same lines as DW8XL (and the upcoming SW4 port). There's still the same enemy pop-in as on PS3 and detail levels don't look like anything was vastly improved, if at all. None of the field of view "enhancements" like DW8 has are in the game, either, although most people will probably find that welcome.
At first glance it doesn't seem like they did anything more than make the resolution 1080P...and that's it. Framerate seems to be same, too. I did notice it hitting 60 FPS on occasion, but for the most part it still fluctuates like on PS3/Vita.
Does this mean that you shouldn't get this on PS4? Absolutely not-- even if the only big difference is the resolution, this is still the best version of the game available. But if you're like me and already own Musou Orochi 2 Ultimate on PS3, I wouldn't recommend upgrading. The difference just isn't as big as the other musou PS4 ports.
Going to keep playing and see if anything else sticks out.