Since the AF is in the camera, I'm not sure why they need more processing power in the lens. Maybe to reduce lag time? 16-bits probably has more to do with the upcoming camera, vs the AFD II and ZD. Having the the AF/MF on the lens barrel is much better than the tiny switch on the body. And the metal lens body may feel more pro than consumer. Mostly, I'm interested in the updated coatings and how the light strikes the sensor.
Has anybody heard what the aperture on the 45-90 is? Contax's was F4.5, but that seems slow to me; F4.5 translates into a pretty dim viewfinder and not much wiggle room when the light starts to wane. The Mamiya 45/2.8 is a small lens & the Mamiya 80/2.8 is a very small lens - so I would think a reasonably sized 45-90/2.8 is possible. Or maybe something like F2.8-F3.5 (though, I'd much prefer a constant aperture). For general walk around use, I agree, the 45-90 is very interesting option - especially if it has a decent minimum focus distance in the 24" to 36" range.
Overall, I'm happy to see forward progress from Mamiya - updated 120 macro, updated 80, the 45-90 zoom, the 150/2.8. If all this makes it to the market, that's alot of new choices. Of course the prices may suck if the new lenses are like the 28 & 75-150. A friend keeps urging me to switch to the Contax mount, but the 645AF and lenses are locked in time. With new lenses being optimized for digital and the bodies becoming more integrated with the backs, I have concerns about the Contax 645AF technology gap in the coming years.