Ok, I played till about the first save point in Yoru no Nai Kuni and I can confirm its not as good looking as other vita titles. Not going to compare it to the ps4 version obviously, but Tokyo Xanadu for example looks much better (so does Sen no kiseki, Digimon, God Eater etc..).
The good news is that I thought it ran smoothly so far (fighting half a dozen enemies with 2 summons and I had no issuses)
Here is me hanging out with Gust-chan :