Re: does nikyo hurt?
I don't think nikyo must rely solely on pain for its effectiveness but saying it should not be at all painful seems to be throwing the baby out with the bathwater. I have never encountered a nikyo that wasn't at least uncomfortable in order to be effective. Certainly, I have never felt a nikyo that was totally pain-free that was also able to control me. Maybe I need a broader experience with other aikidoka.
I am not convinced that a pain-free form of nikyo would actually be effective against someone who was really trying to beat the crap out of you. A pain-free nikyo may appear to work in the dojo where uke has been carefully trained to respond in just the right way, but my experience suggests that such a response to a painless nikyo outside of the dojo by a very aggressive attacker is virtually nil.
My main purpose in commenting in this thread was to object to the idea that a painful nikyo must also necessarily be a poorly executed one. I don't believe this for a moment. The most effective nikyo I have ever felt was also very painful. If some wish to work toward an effective but pain-free nikyo, more power to them. They just shouldn't get on a high horse and proclaim to the rest of us that the proper and best nikyo must always be pain-free.