Below are good resources for understanding the stimulation pattern of hair cells in the semicircular canal.

The thing to keep in mind is that they detect changes in acceleration, rather than absolute velocity. So during acceleration, your hair cells will detect displacement… during constant velocity (over many seconds 10+), your hair cells adapt… and during deceleration (your hair cells need to re-adapt)… This is why one sees increased firing -> baseline firing -> decreased firing rate.

update 11/14/2011: 

An additional point to make is that if you have angular rotation at a constant velocity for a prolonged period of time, the endolymph itself will also eventually begin moving in the same direction as the direction you are rotating your head. Therefore, once you stop moving your head, there will be a lag with your endolymph in terms of it catching up to “no longer moving.” (because it is not directly attached to your head) For example, if you accelerate a car and suddenly stop without being buckled in… the contents within the car, including yourself, will be thrown from the vehicle. A similar effect occurs with the endolymph. The force of the endolymph when you stop rotating your head will will bend your cilia away from the kinocilia, causing hyperpolarization. This is because your endolymph is still moving while your rotation has stopped, a lag time between endolymph movement and head movement.