Looks promising, but interface is way too laggy (toggling or adjusting anything has a delay of a few seconds each time), should be able to click in adjustment bars (brightness, contrast, etc) to jump to an amount vs having to click the arrows over and over (made worse by the first issue), there's no option to automate based on time, and the search box on google.com is almost impossible to see (you would think such a major site would be flawless, much less not have such a huge visibility issue). Also causes significant lag with the whole browser (scrolling pages, switching tabs, etc), which is probably the cause of the first issue, and is by far the biggest problem, which makes the add-on completely unusable. The only saving grace is that the few sites I've checked with it seem to look good, with the exception of the Google search bar previously mentioned. With work, it could be a very nice extension, but it appears it will need a LOT of work. This is with Waterfox 56.1.0 x64 on Win10 x64.

Edit: The lag issue is tied to the use of the dynamic theme. Using static theme has no lag and seems to look mostly good as well. In fact, the Google search bar is more visible, but the sign in button is less visible. The apps button's visibility is poor with both.