First of all thank you for making such a great free open collision and physics library, this is my first post here but I am a long time user of bullet for server side ray casting to do LOS checking and other collisions. Now we are using it on clients for object picking and character control.
Using btKinematicCharacterController with a capsule to control characters and its all working perfect for running around in most cases.
The issues we have are
1: Actor runs into a surface thats too steep, sometimes they can tunnel through the world, this happens much more at higher speeds. Also one time I ran into a wall and got stuck inside the walls collision mesh.
2: Actor runs into a corner and jitters around, this only seems to happen when they are running into two walls. When they hit one wall they just slide along perfect.