For a mod? Pretty stellar in the beginning and it kinda gets lackluster towards the end. Still fun nonetheless, though in later sections playing on Nightmare was definitely not worth it. Reason I say that is because the massive damage increase made hit scan attacks like the final boss's enough to make me wanna break something. The final boss was honestly not being very enjoyable at all. My issues might have been skill related though so I'd recommend a starting run on normal.