Steve and Erick-
I still agree with the idea that bokken suburi is useful and in fact should improve execution of all aikido techniques. But I have to take issue with some of the examples/ways that idea is interpreted here. To explain:
One of my favorite descriptions of aikido is "the gentle art of people folding." It is clear that whether one means the internal or external aspects of aikido, nage must take control of uke's body, often in ways that make him shaped in specific ways. These shapes are used by nage to put force in certain directions, at certain places. If a technique is done right, then uke should indeed go to the ground with minimal effort or motion on nage's part-- because everything is lined up right.
But, let's say you are ending shihonage (as in the example) and sensei puts a sword in your hand (which will demonstrate where your forces are going). If the "blade" looks like it is cutting the upper neck, or the lower neck, or into the head, or from the base of the head to the neck, who cares! The trick being illustrated is that there is a "right" alignment of forces and body parts. It doesn't have to be the case that "right" is always in agreement with a bokken being put into your hands and the blade ends up in a magic place (shihonage is not about uke's neck for instance). For any given technique, "right" might not be cutting uke's head. Or neck. Or anywhere in particular-- those are throws and pins, and it is about uke's balance, not about cutting a head with an imaginary sword. That's my take.
I spent 15 years cutting air with a bokken before I attempted to slice a Tameshigiri mat with a live blade. I had to break all sorts of habits to actually cut it cleanly.
And I spent years doing the rowing exercise without having any idea what its real goal is or how to make it do that for me. But I can't blame the exercise-- funekogi undo works; MY funekogi undo didn't. So, maybe it all comes down to having the right teacher again?