For the last 2 years i have been using a 'V' Blad with a P20 and 40/60/100/180 lenses, most of the time the thing is bolted to a tripod, even though i am a travel shooter, much of the time i used wide apertures, f3.5-f4 and i can assure you that there is no problem with focussing using an Acute Matte screen!!! it's far brighter and easier to focus than the other system i used to use, a Contax 645. The rig has been rock solid in terms of focus and general use, far more solid in terms of focus than the 1DS2 i had. However after spouting the virtues of the system, i have now sold it and will be replacing it with a 1DS3 as the more i travel these days the heavier the Blad and digi SLR system seems to get, and i love the versatility of the shift and fast Canon lenses, which together with an M8 make a light (ish) high quality system. As for the HD 39, i am not it's biggest fan even though i have used Blad for the last 25 years, in my opinion the software sucks, wher the Phase was solid.
Gary.