I've been using the iPad build for a number of weeks and have almost entirely shifted my editing workflow over from Desktop. The only thing left is batch renaming and export functionality.
Edited our family Christmas photos with Darkroom this year. It's amazing to have this much power in a mobile application. This is the future.
Darkroom has been the go-to photo editing app on my iPhone, so I'm very happy that the same simple-yet-powerful functionality is now available on my iPad, too.
It's clear that an obsessive amount of thought has gone into refining common workflows in Darkroom. Rarely do adjustments take more than one or two taps or swipes, which for me makes using Darkroom feel a lot more efficient than Lightroom's many dropdown menus and modes.
This is the only app I use to color grade iPhone photos on my iPhone.