To me anything that is not on the shelf and ready for purchase is just rumor.
MF digital backs, I have found, is one area where you definitely want to stay WAY behind the curve. Like James says above, and I agree, but I would also go further and say "Don't buy anything that's not already on the shelf, is shipping consistently, is confirmed to be fully featured, and also HAS A PROVEN TRACK RECORD".
Look at what happened with the Aptus 75 -- everyone clamoring to get one, only to have it backfire in many people's faces.
Look at what happened with the Aptus 65 with new firmware -- funky white balances, way off.
Look at what happened with the Leica M8 -- same deal, and now, black pants are magenta, and you're facing an official Recall.
I'm sure all these people building these backs are working their tails off to get it right. But we must remember, in the big picture, we're still pretty much in the infancy of digital backs. As knowledgeable as these people are, who are designing them and constructing them, with anything new, surprises are going to happen along the way. It's just where we are in the process.
So take that rule, and apply it toward your back of choice. I just bought a P45, and I actually bought a P45 Plus, and I have a P45 as a "long term loaner" til my Plus arrives. But I had to be clear with myself -- if this P45 Plus never ships, would I be happy just shooting this P45, and using the current 3.76 software? And the answer is a resounding Yes. The P45 does have a solid track record. And when set to compressed Small, you can shoot people very quickly. And when you open the files, your jaw drops when you see the detail.
If I was a Leaf shopper, I'd be looking at that Aptus 22. It's the one with the proven track record. If I was a Phase shopper, pretty much all of them are solid at this point.
One other note that I finally had to reconcile -- None of them are perfect. None of them. There will be sacrifices and compromises with anything you chooose. And some of the compromises are relatively major. If you want easy and bulletproof, choose Canon. Pure and simple. I am a walking testament to that. But I kept having a yearning to get back to medium format, and I chose Phase. Is it perfect? No. Is it like walking around with a giant drum scanner, shooting one frame per second? Absolutely. Gorgeous color, great software, and amazing detail.
Just one opinion.