I'm back from training, and here is my experience. I wanted to test the claim that pocketsticks help with jointlocks, because I train BJJ and was very skeptical that they could have any positive effect. I used a minimag flashlight because the general consensus is that it makes a good substitute. I have never trained in the use of pocketsticks, but I have a good deal of grappling experience and knowledge of joint locks (both in practice and the theory behind the technique).
Holding the pocketstick as it was shown in every picture I found, I attempted to roll with it. I tried to go for moves that seemed like they would most benefit from its use; trapping arms, wrists, ect. In every case the stick was a hinderance. It either hurt my ability to grab, required much extra effort to use, or left me wide open for blows, sweeps or submissions as I attempted to manipulate it. The one thing I found it helpful for was breaking down a person posturing up in my guard, because it increased pressure on the back of the head slightly.
There was actually someone there who had trained a little in the use of pocketsticks, and he showed me a few finger locks. The gave absolutley no control and I was able to escape each one by rolling my wrist. They all required two handed control to set up, and left the guy doing them open to blows. He agreed with me that the locks were not effective.
All this has firmly convinced me that pocketsticks have absolutely no value in grappling. Any benefit they give is far outweighed by the amount of control they take away. Hit people with them, but don't make the mistake of beliveing they help jointlocks.