Goth Mode - too dark in use
Like the concept of a dark mode, especially when working in the wee hours.
Alas it's implementation is unusable as the applications are unoptimised at this moment. Take Mail for example; this fails in dark mode as it fails basic accessibility requirements for contrast, especially if different background/highlight colours are used to identify different email sources. Add to that the problems with rendering "rich text" emails which were designed for a specific colour, e.g. white backgrounds, it ends up as an unusable mess.
So 5 minutes seems to be about it for a feature that's been so pushed.