The one recent (late 2018) publication (1) from that lab hints at the current practical state of the technology:

“We have not (yet) built a full storage system and are currently building out (multiple) prototype read and write heads.”

“the prototype decoder achieves an accuracy of 99.47% across ... voxels written at two micron lateral separation, over 10 layers.”

“we anticipate that in a volume equivalent to a DVD-disk we can write about 1 TB. The technology can potentially get to 360 TB”

1. https://www.microsoft.com/en-us/research/uploads/prod/2018/0...