Originally posted by Miserere I'm afraid not. The Leica S2 is indeed very small for a MF digital (it's smaller than a Nikon D700!), but the Pentax 645D is cubic in shape, probably quite heavy, definitely larger than the S2, and not at all what I would call portable.
I think this was Pentax's biggest mistake with the camera, wanting to make it backwards compatible, and thus preserving the registration distance of the original 645. Leica designed the S2 from the ground up, and in doing so produced the most compact medium format digital camera in the market...by far!
You may not like it, but it isn't a mistake.
Pentax is clearly looking to make a splash with regard to features vs. price. One way to help with that is to actually have a large used lens market. Pentax hasn't been particularly fast to get to market with any of their lenses of late, and without the used lens market, I suspect they'd have zero chance of success, regardless of price.
The leica may may be smaller, but most MF cameras are not, and you don't exactly see leica taking over the market by selling small at a high price point.
The thing I'd be most concerned about is if the electronics are the same as the k-7. USing the same electronics doens't hurt you in a film camera because focusing and metering are pretty much equivalent tasks. In a digital camera, you now have to process 39MP vs 14MP. Unless they have parallel units, you are going to see a lot of the numbers drop with the camera.