Hi Jono,
I know it has been discussed before and I think to understand advantages and disadvantages of both EVF and OVF but personally I am still not a fan of EVF. Even if there are many pluses I feel disconnected from the subject and the real world with an EVF. I think (and hope for Sony useres) that Sony should offer both options in the future.
Of course medium format is a high premium price, and also much slower cameras, but besides IQ itself there is also one other advantage - a big and bright viewfinder which allows to judge focus without additional magnification.
Having said this from the limited experience I have with the A900 this camera has a great viewfinder as well and great IQ. If I was a Sony guy I wonder if I wanted to replace the A900 with an A77.
IMO High ISO are overrated anyways. If one has good and fast glass one can do quite a bit even with ISO 640 and lower.
But lets see what it really is.
HI Tom
Whilst I quite agree about the big bright viewfinders and the troubles with EVF, I've never heard anyone saying that's what they're using MF for. I wonder how good an EVF has to be before one ceases to feel disconnected? Added to which, there has been talk of the A99 having an optical option as well (have to wait and see)
Practice is another issue, as is general ergonomics, and of course, much of this is personal.
My point really was that if something which filled the bill technically for almost all situations was available in a reasonably sized package, then it would become increasingly difficult to get people to pay 15 times as much for something which added quality (but quality which one mostly didn't need), but removed functionality, and at that point the price differential will get even bigger.
Sony don't really have the lenses to take over from Canikon yet, but I can see the A77 taking over from the Canon 5D and Nikon 700 for that vast horde of middle of the road wedding and event photographers (if not from the top of the road photographers like Marc, who are using MF as well).
What's grand is that after a feeling that everything was settling down to 12-16mp cropped sensors and 12-24mp full frame sensors; suddenly we seem to be living in interesting times again.
all the best