I bought the P30 before I ever used a Hassy V. I bought it solely to get into low night long exposure imaging, which it does very nicely. I have taken exposures up to 5 mins: http://www.5pmlight.com/?p=2136
The reason I am selling it is ... to get more gear :-) Specifically, I want a more portable solution so I can use it for landscape work. My favorite camera is actually the XPan, and as good as the Leica M9 is (which I have), once you crop, you are losing bits, whereas a MF sensor will hold up better.
The P30 is really at the sweet spot. The next step up is at least $8000 or more. It has plenty enough resolution.
The only caveat is that for the V, newer lens (CFx) works better than old C lens, and for bulb exposures, some of the newer lens shut off the sync signal in between open and close to save energy and this is bad for the data back. However, it's a simple fix for Hassy to do.
If you are a Hassy shooter, you will be amazed how well your Zeiss lens look in the digital age.