I think his voice has improved and for a sixty year old - he has amazing pipes. But, we did miss an opportunity to hear the great instrument of his voice when he was in his prime.
His voice around 69, 70, and 1971 was amazing and i feel cheated that we never got to hear Paul in the prime of his vocal range do some of the great Beatle and Wings songs.
I watched an Elvis Presley special from 1970 and his voice was phenomenal (probably because E never smoked) - Elvis at 35 had a voice that was quite simply - awe-inspiring. One thing Elvis never lost even during the drug and obesity was his incredible voice!! The myth of Elvis would leave us to believe he never recorded another good song after he joined the army per Lennon/Paul. That is simply not true. Elvis released some decent material in the 70's but he did release some real crap too
How cool would it have been to have Paul M in 1975 produced an Elvis album??? Elvis singing "That would be something", "Dear Friend" "Band on the Run" or "Maybe I'm Amazed" or even something as fruity and light-weight as "Love in Song" ...Now, that would have been call.