I said he was a poor teacher. Although he may have taught the Uchideschi, people I have spoken to say he didn't really 'teach' at all - He wouldn't say anything negative about the techniques you were doing, and therefore didn't direct people. Also, he didn't teach in a structured way (which some people may argue is better).
Also, it seems he awarded several people 10th Dan in private. Either they are lying or he was being somewhat sycophantic (or maybe just saying what they wanted to hear).
Persoanlly I believe he was a fantastic martial artist who wasn't willing to teach all that he knew (for example striking vital points was not a part of his training though he undoubtedly used them himself in real many real challanges). He also spoke in a traditional form of the Japanese language which was hard for many of the Japanese to understand.
Unfortuantely great martial artists are not always great teachers. I have seen many fantastic aikidoka who have very poor students.
Therefore the real test (of a good teacher) is, did any of his students exceed him? I don't believe they did.
Why was this? I think he created a new martial art aimed towards peace which was less effective than his own capability. I think he hoped to create a peace movement, and he also feared that what he knew would be cause his own destruction, or that of others.