I just found this in the Insider's feedback. If you hit Ctrl T in the Store it will switch to a dark theme! Sadly, it doesn't seem to do this on any other apps.
The registry hack from a few builds back that gave us a more global dark theme has been disabled. Instead of fixing the two minor display issues from that they just disabled .
The registry hack from a few builds back that gave us a more global dark theme has been disabled. Instead of fixing the two minor display issues from that they just disabled .