Thank you very much for the comments! Some further notes:
1. I have the cousin lens FA 35mm f/2.0 and I was looking similar performance in a longer range. This lens was to complement my 35mm and 70mm (Sigma macro) primes in between them.
2. I expected it to be soft wide open (like many fast lenses) and I should have read Klaus's review, which actually tells it exactly. But it was worse than I could anticipate.
3. I think my copy also has some back focusing, as I find it often hard to get sharp results on close subjects, regardless of how small aperture I use.
4. I was hoping to get a good low light lens, but this is not it. It seems that this is not even a cloudy weather lens.
5. About the bokeh, I find it most of the times nice, but it can be distracting also.
6. Nevertheless this lens can be excellent in good conditions, i.e. shooting subjects not too close/not to exact focus spots and shooting in bright sunlight. I'll just have to learn how and when to use it.
There is still something I like about it, but my search for the Holy Grail continues
Some more pics for these notes, all shot at f/4.0 or f/5.6 with this lens:
#1 Pleasing colours, decent sharpness
#2 Nice, but the DOF plane is not quite where aimed
#3 100% Crop, spot focused to the bug (back focusing)
#4 Rather nice bokeh
#5 Not so nice bokeh in a contrasty area