my understanding is that the engine continuously sends information. There is thread by shoreviatom (forgot his name), it explains how if I send information to the server, i'll just be recieving something i sent before.
For example, I send my current pan (23) on frame 1, by frame 2 i my pan is now 26, on frame 3 I recieve the 1st pan back which is again 23, even though i was trying to move to 29. This causes that glitchy/twitchy/laggy look. The delay between sending the information and when you get it back isn't exactly constant so one time it could take 1 frame the next time it could take 2 frames, the 3rd time it could be 3 frames, the 4th it could be 1 frame again. REMEMBER your sending and recieving information for the same entity.