There are probably hundreds of thousands of speed controlled cylinders in auto assembly plants world wide.
With a suitably sized cylinder for the application, they will run so close to a constant speed, you will never know the difference. Kinda like turning on an LED with a car battery, the voltage doesn't flinch. You can buy/make a simple/cheap "speed control" (that's their real name) that attaches to the cylinder ports. Those along with tailoring the supply pressure will make the cylinder very speed controllable.
Because they're mechanical, nose seals wear out quite often, piston seals not so much. A lubricated air supply helps too.
To do what some of them do electrically would cost almost 50X as much.