I've been really impressed with it so far. My experimenting with the engine has been limited because I'm busy with my side of making the app (what a fun discussion that'll be on these boards). That said, I have found that if you're making PBR texture maps in apps like Quixel Suite or Substance Designer, a glossy/specular setup works well. I haven't tried metalness/roughness but since the glossy/spec works so far, I'm not inclined to pursue the other method right now.