Nice! I've had mine out to the beach here on the west coast a few times. It performed really well. I couldn't take it out into the soft sand too far as I didn't have a flag, but in the smaller dunes it was great. No airing down either, just sand mode and center diff lock.
I just tried mine out and now I get what you're saying - when you turn it off it comes back on the next time you open the hatch. At least it remembers the brightness setting.
I had the same issue as YellowLab - it seems like some of us have ACC Customize on by default, and others off. It's such an ambiguous name for a feature, but I'm sure it's in the manual.
I haven't tried to turn mine off yet - is it not responsive enough?
And to anyone interested in these, it's very bright. In fact, I found it too bright on the highest setting so I dimmed mine a bit. You just touch the light (and hold) and it starts dimming. Great feature.
You can have the dealer turn off the seat belt warning for free at your 6 month / 5k mile service. I'm not aware of the ability to turn off only the rear seat warning, though.