We used them all season long last year. We had a catapult ball shooter. The cradle that held the ball had an arced "tusk" that could be moved to three different position to affect our release angle.
Our source code (with ascii art) is available here:
https://github.com/Team2168/FRC2014_...ems/Tusks.java
Note that the way these components work is there are two rods which are not coupled to one another. The middle port on the actuator extends the external rod, and retracts the internal rod. As a result, if you're trying to move the actuator to the intermediate position, you'll need to sequence the move, otherwise you may not allot enough time for pressure to vent to atmosphere. It's hard to explain in words...
You can see how we implemented this sequencing here:
https://github.com/Team2168/FRC2014_...tPosition.java
Our plumbing was also a little more complicated than normal for these. As we used two double solenoids, so it required a check valve to be installed in line. If you need a pneumatic schematic, PM me (as I won't see requests in this thread) and I'll document what we did on our robot from last year.