Thanks for your answers guys.
Seems like the P30+ is a sweet back. To be honest the only thing that turns me off slightly is the 1.3x crop. I really like the compressed depth / 3D look you more easily see when using bigger sensors / film. I like the sound of the P30+ mid range ISO capability being better than most which, although I mainly sit at 100ISO, will be important to it's versatility in use, especially if needing to work hand held.
To further explain the type of work I want to do with it; I'm always in the field. I shoot mainly what people would call social documentary / street photography. I walk the streets - rain, hail or snow - and photograph independently of assistants, computers etc. Everything is taken under natural light, with the occasional (badly executed!) use of flash. I like the idea of MF digital for several reasons. By and large, I like to take my time when I work. I'm usually on a tripod these days and I don't fire off thousands of shots. The type of work I do also requires I give something back to gain peoples trust and also say thanks. With film (I've been loving using a Mamiya 7 kit for four years, as well as 4x5",) It takes a long time to get photos back to the subjects and by the time they get them a bond / trust is often broken. Digital is just quicker and more helpful in this regard. I also feel adding a digital MF back will be a positive step in becoming wholly independent from any labs and technicians that (sometimes) don't meet quality expectations. I'm sick of couriering film out - you've got two sets of couriers to worry about, the lab staff etc. Lastly, the cost of shooting film is now insane. The quality and look of the final result from film is just not an issue, for me it's perfect, but when you can't afford to shoot a lot and take risks, well, what's the point?
Anyway, I appreciate all of your comments. What is the going rate for a P30+ these days in the US? The market here is really small and thus prices are usually a good 50% more, with little support network to justify it...
Tim