I too have the Phaseone camera and have noticed this.
I was shooting some dance artists in mid flight (jumping) last week and it proved to be very hard to judge when to press, but after a while you get used to it. I will check out the short latency thing when I get into the studio.
Also I do find that occasionally the camera will expose an image wide open, only a few times in the 600 captures that I have done so far.
In spite of all the above, I love this camera, for me, it's so much nicer to use than the Hasselblad V that I traded it for which was too hard to focus unless tethered....
Steve