Hey there! Perfectly understandable. For my part as the designer, I've playtested A Nocturne many times through a mix of one-shots and multiple lengthy campaigns. The game was in development for several years, beginning in the early days when Blades in the Dark was only just out and there was still the Blades Google+ community, so I've had plenty of time to go back and forth over the design to make sure it's doing what I want it to be doing. However, I know mileage may vary, and I know of a couple different groups who've given me feedback, so I'll let folks chime in here with their thoughts.
I'm going to chime in as someone who loves the game and spent a long time playtesting GURPS stuff. First, it feels like it's been played a lot. But it doesn't feel like it's been widely played.
Just tinkering with the rules as a reader and would be player, they work. But they require some thought and interpretation. As well as some familiarity to know where things are in the file.
It could really use a quick and dirty summary set of pages, a table of contents and an index.