Here is how DP Review explain it.http://www.dpreview.com/reviews/olympus-om-d-e-m5-ii/4
You can draw your own conclusions from how you would use it, but no more than ISO 1600 and F8, plus the subject needs to be motionless makes it a bit of a gimmick in my book for general use.
But for the right application it does expand the cameras capabilities.
RAW files are usually around the same size in mb as the mega pixel count, this feature leaves you with a 100 mb file from a 16 mp sensor.
The Sony A7RII is the mirrorless I would put my money down on if you want hi res. Better than half the RAW file size from it's 42 mp sensor and no usage limitation.