Average at best, awful at its worst. It has a lot of problems. For one thing, the level structure is sometimes almost too easy; I had a level set where the rooms with the key and locked door were adjacent to one another... not exactly a challenge, y'know?
Another problem I just experienced is "shotgun jumping" up to an otherwise unreachable room only to have a spider drop on me and instantly kill me. Like, how am I supposed to react to something that happens within the span of a handful of frames, when my weapon is on its brief cooldown from launching me upwards? And in addition to those dubious enemy spawns, I managed to screenshot a room where a spider-like enemy spawned inside a wall!
Third, I really have to wonder how these levels are generated, because after another three brief replays, I happened upon a room that had a downward exit... but the pathway to reach it was just a few pixels too short and I couldn't reach it. Now just imagine... if I had collected a key to a level, what would happen if that was the only path to the locked door? Why, I'd be rightly fucked, wouldn't I? I'd have to die and start all over. And if I'd killed all the enemies in the current level up to that point, I'd be shit out of luck.
It's honestly terrible. It's every other procedurally generated platformer, only this one has the added "feature" of not testing whether or not a level is actually BEATABLE before putting the player into it, and no way to prevent unavoidable or inexcusable player deaths.