I could see using it as a "transport station" between bases... Fill a bunch of chests with resources at Base A, activate it and all the chests move to Base B.
Just a first impression from Dire's video.
I suppose the "invisible on one side, solid rock on the other" might make for some interesting traps... Do Endermen see at the quantum level? Do they check for appropriate space to teleport to from the floor up or ceiling down? If the former, could they be tricked into teleporting into a quantum block that turns to stone as soon as someone looks at it?
Interesting questions, and I'm sure we'll se experimentation.