I love Night mode.
I've been known to walk out of my darkened edit bay and screech "THE LIGHT! IT BURNS!" Every time I talk to the Google Play Music team, I beg them to return the dark UI the app featured when I first joined Android. But not everyone wants everything to go back to the Dark HOLOYOLO ages, though, so if/when Night mode makes its grand return, it needs to do so in a way that can please both the dark-loving users and the light.
Nova Launcher gives me hope that we're getting close to that.
Night mode was hiding in the Developer Preview of Android Marshmallow, but never made it to the final release. This year, Night mode is back and while you have the option to use a dark mode for the Android OS, there is no such option for Night mode to trigger dark themes in other apps. Nova Launcher's new night mode hasn't let that omission stop them from tying their Night mode into the Android system.
The Follow system option for Night mode will switch between dark and light themes just as the system does. If you're on the Android N Developer Preview, Night mode will switch as your system does, if your system does. If you're on any of the publicly released version of Android, from Marshmallow down, Follow system acts currently acts like Auto, meaning it will switch based on your time/location and the sunset time.
This isn't a perfect system. The lack of a clear-cut off switch for this feature might run afoul of users who don't care for the dark theme or find it harder to read. On that note, if you don't want night mode on, you'll need to set a Custom timing for it, such as from 3:00 to 3:05 AM when you'll likely be asleep and never see it.
The implementation of dark mode outside Nova Settings isn't perfect quite yet, especially for people using custom color/tints for their app drawer, folders, and other elements. Night mode currently wipes out all those lovely translucent tones and replaces them with the same dark grey that's used in Nova Settings. Thankfully, Night mode isn't an all or nothing affair.
Night mode always applies a dark theme to Nova Settings when active, but you can turn it off for all or some of the visible home screen and app drawer features it can affect. Getting a dark search bar outside Action Launcher might be reason enough for some users to turn on Night mode, but you may not want it plastering dark grey over your app drawer - or even worse, changing your custom app drawer icon to a boring, standard (but dark) one.
The control over individual features in an important one, and one not often found in apps that are gracious enough to feature a Night mode. Much as I love dark themes, they don't work perfectly for all features and screens in all apps, so you'll have to turn it off while using a particular feature or trying to use the app in particular situations. We need more granular controls for Night mode, and while that most certainly means more work for already hard-working developers, the dividends for users can be tremendous.
I will say that Night mode in Nova Launcher could still use a few more options, such as letting users switch from the more material dark grey to a pure black, especially for AMOLED devices. But it's already three steps in the right direction, and I can only hope that more apps start following its lead.