A friend just came back from an LBS fitting. While there he had some ceramic wheel bearing installed in his rear wheel. He said that the rear wheel seemed to spin forever when up on the stand and he was told that they are much more durable than stock bearings. When I asked if he could tell the difference on the road he said he wasn't really sure. So, I just got to wondering if anyone here is using them and if you can feel a significant difference on the road.