@ David B: I feel exactly the same way.
My first audition of Pianoteq was version 2.5 ... more than ten years ago. It sounded utterly terrible. But no worries, I thought. I knew that this tech was new, so I had hopes for improvement.
I then tried version 3.0. This was markedly better, but still quite poor.
Then came version 4.0. There was little change from v3. I was disappointed.
Same story for v5, v6, and v7. None were anywhere close to acceptable. Very disappointing.
It made me wonder why they decided to "branch out" and start producing a Steinway, a Grotrian, a Bechstein, a Petrof, a Steingraeber, and a Bluthner. Why produce six piano sounds when you cannot even get one to sound like a piano?
It's also strange that some people dislike the bass registers of PT. I find that the low end of PT is the least objectionable.
Similarly some complain about the top octave, yet I find it not so bothersome (though that may be because I use that octave so very little).
All of that pales, though, compared to the abomination of the middle four octaves ... which is just where most of the music happens. That sound is an insult to pianos and to pianists. If that sound were the only piano sound available to me ... I think I'd take up the banjo. Or the one string fiddle. Or meditation.