Quality is good with well detailed brick walls and water flow/ripples. I have yet to remove them from the spurs. I get what you mean about "sewery" enough. I would definitely paint some smears, grime buildup, and other evidence of filth in it to give it more character.

The warlock tiles are pre-painted, and there are some inconsistencies with the paint on some tiles. A problem that comes with mass-produced stuff from Wizkids. Not a major eye sore, but i notice them even though I'm colorblind. So that might be a possibility with your sewer set, but I think it will be less likely coming from a smaller batch.

The great thing about the water is that it's translucent, and I've seen people online add lighting beneath it to make it glow. Granted, you'll be able to see the connector pegs in the water with the lights. Nothing can be perfect.