Definitely looks very useful! Is the live view working the same in all lighting conditions or does it work best in just some like the older backs?
We will need several days more of testing since "all" is very comprehensive. However, so far I can tell you I have not run into a situation with any significant issues. In very high contrast scenes the back requires a 1-1.5 second adjustment period when you scroll from a very bright area to a very dark area, as it does form of auto-exposure on screen, but this is, to me, not a problem for the use-cases we're describing (focusing, composition, subject arrangement).
I have not tried at night yet, though CI reports they have and were able to focus accurately. I have tried dim city light (after sun was behind buildings) the 100% view was modestly grainy (in the least it was visibly more grainy than in bright light), but refreshed very fast and posed no challenge to fast and accurate focusing.
