The 900 looks impressive, especially considering the price point. The best part is the full-frame sensor. The pixel count is impressive but, like the 1Ds Mk III, is creeping into fantasy land. It takes an extremely sharp lens to take advantage of anything close to 25 MP.
I love shooting digital, and the immediate feedback and low operating cost has helped me immensely with my photography. However, after drooling over every full-frame body from the Canon 5D to the Mk III, I decided to go the old-school route and switch back to film...at least for making larger prints. I can scan the equivalent of 300 megapixels from a 6x7 medium format frame (if I ever wanted to) and I can develop my own negatives in the bathroom (gotta love TMAX 100). Realistically I could never justify dumping even $3000+ into a new camera body, and that doesn't even count the high-dollar lenses it would justify. I can scan sharper images from my Mamiya than I would ever get from a digital SLR.
I still rely on my XTi for chasing, action, and any situation where I don't have time to manually meter the scene with a spot meter. The image quality is great for its price range, and it makes really nice prints up to 11x17.
Having said that, there is something extremely satisfying about taking the time to manually meter the scene and fire off a few images with the Mamiya. When I can get the shot, the image quality blows the XTi away.
So, the point of my ramblings is that something like the Alpha 900 or the Canon Mark III may make good sense for someone making a living with it. For most of us, though, there are much cheaper options that can beat them on image quality. Studios are flooding the market with used medium format gear.
