I have indeed stayed with it. For about eight years.
These things take time; stay with it, play with it.
I've tried every demo release of Pianoteq since version 2. That version was intensely horrible, and version 3 was almost as bad. Versions 4+ are better, but still they all sound fake.
I know what it is so sit in front of a proper acoustic piano, and yet the sound of Pianoteq is that of a piano that is set "somewhere else". It's not here. It's in another room. It just doesn't have presence. (And that's just for the lowest four octaves. The upper three have an even less satisfying tinkling tone that I find abhorrent.)
I wish Modartt would stop building model after model (Steinway, Steingraeber, Petrof, Bechstein, Grotrian, etc.) and instead focus on making just one of them ... just one ... sound like a piano.
Perhaps the problem derives from my dislike of the modern pop piano sound? A piano that "cuts through the mix" does not interest me. I'm only interested in the sound of solo piano performance. Authenticity is no never mind for many forms of modern music. But it matters a lot to me.
Elsewhere on this board, when discussing sampled VSTs, there are fussy discussions over the lack of proper half-pedaling, the tech-derived dropouts and clicks, the inadequate dynamics, and on and on. These things are important. But they are mere flaws in an otherwise almost-real sampled piano sound. They are minor crystalline inclusions in an otherwise flawless diamond. Whereas Pianoteq is a piece of broken glass pretending to be a gemstone.
It just doesn't work for me.