There is one big omission in this article, which seems to focus mainly on hydrodynamic computing: "static" hydraulic computing, as implemented with relay valves --- and found major application as the control unit of passenger car automatic trnsmissions throughout much of the last century, before electronic controls became common. Examples:
When I was a kid I used to make walking Lego models using Lego pneumatic elements and pneumatic logic to synchronize movement. My experiments eventually culminated in a (extremely slow) Rubik's cube manipulator which used a couple of first generation Mindstorm RCXs to "solve" the cube by reversing the shuffling stage.
http://cogpro.com/chapters/M-ThreeSpeedHydramatic/images/M%2...
http://oldcarblog.com/manuals/1970/1970%20Service%20Manual/1...