Just want to say thanks to everyone here - I have successfully updated my De La Vega rooted MI9 to NC2. Woot! Since I have simple needs (just want to debloat and wifi tether) I originally planned to update to stock OTA KitKat then use TowelRoot, but my phone refused to cooperate. It wouldn't even complete the OTA MJ5 update, and I couldn't get it to fully unroot using SuperSU Pro - even the Samsung guys at Best Buy couldn't flash the update for me. So I started looking into alternatives and after many hours of reading threads here decided to take the plunge. So glad I did. Everything went smoothly.
Well, except I had the same problem some others have had where on the initial boot the touch screen wouldn't work. But I remembered others saying that the pen worked, so I tried that. Problem disappeared after a second reboot.