Re: What is "Aikido"?
I think Tim is correct, but ultimately application will depend on how the person trains.
Here's my take it:
The manipulation of internall pressures/tensions allow Kuzushi on contact and is VERY effective when using sword. I found that out the quick way by testing some stuff out with my friend whose done Iai/Kendo for 7+ years now.
Sword vs. No sword means you have to move with "setsuna." That requires you having the "connected" body, and being able to manipulate the pressures in the body in one "feel". This allows extra leeway for timing since you apply kuzushi to the person simply by touching him.
(To the other guy it just looks like you raised your arm straight up, but somehow his blade is still deflected, and he's way off balance)
To answer David's question, use of the internal pressures allow you to make slight minute adjustments in your own body simply, almost indicernable to the outside viewer, but with the result being that you still take the guys center on contact and hence his sword as well. (All the while not "resisting" against the line of attack)
Granted, that's a simplistic explanation.
It still helps to be grounded in the ideas of "men kara sen, sen kara ten" or rather "area to line, line to point" concepts, which lead into go no sen, sen no sen, connection differences between hai men (back/yang side), zen men (front/yin side) and all that jibe.