What actually is interesting to me is the talk about aiki lately, found at these forums and elsewhere, as a form of internal training/power and how it is different from the standard aiki (of timing and blending type also referred to as ki no musubi - tying your ki with that of your partner). However, it's quite clear to me (and Saito M sensei talk about this as well) that the aiki of aikiken, as bequeathed by the founder, was not so much of the former kind (IP) as that of the latter (ki no musubi).
Jacob - This is a really important statement. I think you are absolutely correct, in so far as Saito sensei's weapon's work, and all of it's off-shoots. However, let me add a caveat. Note this video
Through most of it, Ueshiba is doing the blending you are talking about. But here and there, he demonstrates internal strength. We have two alternative explanations, in my view:
1. Ueshiba M. only wanted to teach the blending/musubi, which comprised most of his demonstrations, but to demonstrate his mastery/how wonderful he <alone> was, he added these internal strength manifestations that he learned from Daito-ryu.
2. The organization of the body and mind that occurs with internal strength training is absolutely essential to achieve ki no musubi abilities at a high level. Those abilities enable the practitioner to elicit certain responses from aite which are NOT dependent on them taking "good" ukemi or becoming a "dive bunny."