I said I'll be back with some news, and here I am.
I got a new copy of this zoom after a one month out-of-stocks delay.
This copy don't have the great problems of the first one, and works much better.
Someone asked me why I scored a 3 if my copy was a bad one, and I answered people may know that buying a $1,500 lens, you can get a potatoe. Even if you can get it changed.
Tests with new copy say that at 2.8, you don't have good sharpness, better close a couple of diaphrams.
Results are good, no doubt, but not 1,500 dollars good !
The 18-35mm 3.5-4.5 gives me more sharpness. Strange, isn't it ?
Anyway, I had the new copy less than a week. I sold it yet. But let the lens a long week end to the buyer for him to try.
He felt happy, and so do I.