Well, I practiced for Nishio sensei and tried to understand his aikido for a couple of decades. There are definitely lots of people who pracitced more for him, and understood more.
His aikido was a very complex and advanced system, making anybody feel like a beginner, whatever other aikido experience they had.
There are some of his senior students travelling the world, teaching aikido - more or less according to his principles. Some of them don't agree with each other about it. Well, that happens.
I guess that the best to start with, is to watch films of Nishio sensei himself. For example, I put a set of five videos from a seminar he had in my dojo on YouTube. Here is the first one:
http://www.youtube.com/watch?v=IEZWojpNnao
About Nishio sensei's
tegatana (hand-sword), I can tell you that it worked excellently on me
He talked about
atemi-no-kokyu, which I would guess was a way of emphasizing that any atemi must be done with distinct spirit, and also that if done so, it definitely creates a reaction in uke.