Re: Pain in aikido?
Reliance on pain = bad. Excessive use of pain to the point of damage = bad. However, in general I agree, the use of pain is fine between consenting adults (and I believe mandatory in certain dojos, the wee scamps).
For me, pain is part and parcel of various moves and should be used (or at least be available) for emphasis, just like atemi. Also, I wouldn't consider moving prior to the pain setting in being a bad uke. If nages entire technique is Dependant on inflicting pain I would move prior to the pain to a point where I can hit them - sorry, I meant remonstrate in a kindly yet vigorous manner. If my centre is not being taken, I'm not interested in staying around for the crunch.
Caveat - don't use pain in your techniques unless you're willing to accept it back - favourite niggle of mine. As they say, everyone should get a fair crack of the whip.