What a difficult post to respond to. I have to declare a bias right at the start - Ashkenazy is a friend of mine.
First, the Beethoven Sonatas. I think that the main problem is the recording lable. Decca were characterised by their own sound quality. To my ears it is rather dull and uninspiring but it was the particular quality that said "Decca".
A second difficulty was that when Ash first came to the west he was pressured into recording an excessive amount in a relatively short time. This was pressure from the record company rather than his own choice.
For live performance he will not play any work that is unrehearsed in front of even a private audience. In this respect he is a perfectionist. I am told that even on holiday he hires a piano so that he can get in his daily practice.
In the 1970's there was a long running series on BBC television on the piano. Ash was the guests for one of the programmes. When break time came during the recording the presenter and technicians were exhausted but Ash simply went off to another studio to get an hours practice in.
He has been to my home several times

. While I have been talking with his wife Dodi, he has gone off to practice on my piano and I can assure everyone that he is capable of an amazing variety of tone colour and expression. (As an aside, I asked my wife not to clean to piano afterwards so that I could absorb the sweat from his fingers with the hope that some of the genius would be absorbed - it didn't work

).
Ashkenazy is one of the nicest people that I have had the privilege of meeting - very relaxed and very intelligent. It has been the greatest honour to me to have had the pleasure of knowing this amazing man and I feel blessed to have known him. It was through listening to his earlier recordings and recitals that inspired me to want to learn to play the piano. To me, his earlier work was a revelation. Sadly, I do not think that we shall have the pleasure of hearing him live any more. His hands cause him some discomfort - not enough for the listener to notice but enough for him to know.
Finally, a small anecdote. During one conversation I mentioned that he never played any Bach. He responded by saying that he did not feel that he was a Bach player. Some time later he releases the complete 48p&f! I would like to think (but very much doubt it) that I had a small part to play.
Although I have not managed to meet up with him for a few years now but I still receive a regular Christmas card and occasional letter.