I would agree with Matt, and have recently queried how I should be doing ikkyo. The question is, do you lead ukes ki down his arm, or do you push through the head. I have always learnt it where you push the elbow through the head and very importantly to 'crank' the elbow in a circular motion to drop it below the wrist as soon as possible. This is very powerful and the attack to the head breaks ukes balance very quickly, acting on the base of the spine.
Many people would disagree with this saying that it is non-aiki (although you could refer to aiki-jitsu, which is just the same). Some practitioners direct uke down by walking forwards or by directing them in the direction the uke's arm is pointing. I would disagree with these methods in most circumstances. In both positions the elbow is level or higher than the wrist, allowing uke either to hold himself there (putting his hand on the ground and stabilising himself) and therefore put up a struggle, or even worse, to drop his (bend) elbow and counter the technique.
To me the first movement should be very powerful and dyanmic, so that ukes shoulder is very low and completely controlled by his locked arm. It is a similar position to holding a lowered sword, which you then drive into the ground point first to pin his shoulder.
However much I try the other techniques I always end up running around the dojo with the uke - ineffective. The only time I would lead uke in this way would be if there was a strong forward resistance by uke to the technique, at which point it should still be a sharp cut down (with the ura movement). Considering that most peoples reaction to a grab is to bunch up (pull in their arms and withdraw their body) the first technique is almost always the most effective. I no longer practise the 'leading them by the arm' type. [basically there is a mechanical problem with this -> it only works if there is a strong moment down the arm, and this cannot be generated by tori/nage because such a strong directional pull will install a counter reaction by uke].
I hope this is contentious, cos I have been wrangling with this for a long long time!