Since there seems to be some interest here in the Sony A900 (I know I'm sure as heck interested), I thought I'd mention that Michael Reichmann
announced just yesterday (December 22) that he is taking the A900 to Antarctica as his main system:
As this is published in the third week of December I have been working with the A900 for a bit more than a month. I have gained enough confidence (and admiration) for the camera at this point that I plan on taking it to Antarctica in January as my main system for the trip. My kit will consist of two A900 bodies, one with the vertical grip, and six lenses, the 24-70mm Zeiss Vario Sonnar, 50mm f/1.4 Sony, 70-200mm f/2.8 Sony G, 135mm f/1.8 Zeiss Sonnar, 70-300mm f/5.6 Sony G, and 500mm f/8 Reflex Sony.
Interestingly - and I am sure quite coincidentally

- today
Mr. Reichmann announced the sudden appearance at his doorstep of a Canon 5D Mk II, and the promise of a Nikon D3x in time for his trip:
Yes Virginia – there is a Santa Claus. Within the past 24 hours I have received a 5D MKII from Canon to take to Antarctica two weeks from now, and Nikon just called to say that a D3x will be available as well.
Excellent news, and my thanks to both companies for making these cameras available for some serious field testing.
I will be bringing a Sony A900 system as well, so it now looks like I'll be able to shoot with all three new systems side by side on this trip.
I think Mr. Reichmann's Antarctica trip report is going to make for some VERY interesting reading!