MtnGoat --
I know a guy who has used these in the third world for filling impoundments used for milling grain, potable water and watering cattle. He was making pumps out of standard pipe, fittings, and small propane tanks. The cost of the pump can be very small -- it's the cost of the pipe up to the impoundment that can get prohibitive. I know because he hit me up for a donation to buy drive/delivery pipe for a project he was working on.
High head flows allow smaller pipe diameters and less $$$. The specific application he was using them for was in mountainous areas that had spring runoff and sporadic heavy rains interspersed with dry spells. They pumped the h2o uphill during periods when the streams flowed and ran it down through a grain mill and then into cattle tanks during dry spells.
As BMT pointed out, the knock on effects from this were enormous -- more milk/better nutrition for kids, healthier cattle, more free time for women to start small businesses for cash, etc. etc.
I will track him down and PM his current location/email. I had his plan for building a ram out of standard 2" and 4" pipe -- I will try to find it.