I have also owned my ZD for a couple of months. I am very pleased with it. Like most cameras, it has some faults, but the positives are many.
Image quality at low ISO is very high, at least the equivalent for good 6x7 drum scanned film (I have a drum scanner and used to shoot 6x7 film so I think I am qualified to say this). In its standard set up, it has no AA filter, so images are sharp and detailed, but you get occasional colour artifacts at the limits of resolution. These can be removed by using appropriate software, and generally I don't have an issue with this.
Dynamic range is also high. I use the camera for stock photography landscape etc. Its not a fast camera, so its no good for sports.
On the negative side, the rear screen is poor, with no 100% preview. All its good for is checking composition and histograms. I have no idea why Mamiya did not include a better screen, but maybe its to keep heat down, or maybe its a cost saving measure. You get used to it, and shooting tethered in a studio, its not an issue.
If you compare the ZD to some other medium format solutions, it looks like, and is, excellent value. As Ivan said, the price, compared with other megabucks solutions, takes the angst out of buying (although its hardly cheap). Its just a big dslr, with vastly superior image quality at low ISO.
I posted some samples in this thread:http://luminous-landscape.com/forum/index....showtopic=11724
They are not perfect, but give an idea at least of performance at just above base ISO.
Also read the most recent ZD review on this site, as its quite useful.
I strongly recommend using SilkyPix raw decoder with the ZD. Its better than the bundled PhotoStudio (which is OK). Ramp up the quality settings in SilkyPix to the max, reduce sharpening, and its a quick and efficient way to work, with great results. I rate SilkyPix above any other raw decoder currently available for the ZD.