This isn't for anyone. _Anyone_. Beyond the 300-350 pixels per inch, the 'sharpness' and the 'detail' is not perceivable by human eyes. It's a wastage of power, memory and CPU/GPU resources. This is what happens when Marketing dictates Engineering.
Granted, with current technology we have single-coloured pixels, so 300 ppi is really 3-900 dpi (or pixel-parts) -- that might have something to do with it?
It's maybe most comparable to the 15" Retina MBP--roughly similar density (220 vs 231), and both are bigger panels you use at a distance.
Just interesting that from a pure spec-wars perspective, raw density isn't one of the dimensions on which the Toughpad is pushing the envelope. Density in its size class, maybe, but not density full-stop.