auspicousdragon.net have a short review of the Leica R9 and DIGITAL-MODUL-R 10 Megapixel digital back.

“mirror lock-up: this is really how it should be on all cameras. A switch (not a button) on the camera takes you from normal to mirror lock-up mode. In mirror lock-up mode you have to fire the camera twice to take a picture (using any of the shutter triggers or cable releases). The first trip puts the mirror up. The second takes the exposure. This means you have complete control over how long the mirror is up, and you can decide exactly when you want the exposure taken.”

Website: auspicousdragon.net - Leica R9 and DIGITAL-MODUL-R Review