So, if the A77 has a purely electronic viewfinder, what's the mirror there for?
Just for the AF system? And if so, why is it half-silvered and not fully-silvered?
I think it's just fot the AF system, and it has to be translucent because it doesn't get out of the way when taking pictures (or feeding an image to the live view LCD/EVF)
this means you lose 1/3 stop of light on the sensor; but it also means it's much more difficult for dust to get to your sensor (eventually, it will get there, and it will be more difficult to get rid of it, but that probably will take longer than the camera will stay with me; in the meantime, I'll be much less worried when changing lenses in a windy day in the countryside: the mirror is much easier to clean than the sensor)
edit: another nice thing about this translucent mirror tech: AF doesn't stop working while you're taking pictures, so this one shoots 12fps whith autofocus
as seen here: http://www.amazon.com/gp/mpd/permalink/mL6KZXE96MW1
now, about those "canon and nikon will bring out something similar soon" arguments...
what you're saying amounts to: "yes, those iphones and android thingys are great, but nokia surely is an amazing company, my last 4 phones were from them and they were great for their time; they surely will respond with similar specs" - or will they?
if at least canon and nikon showed us what they're working on, maybe, just maybe, I'd be tempted to wait for them; if they don't bring anything out, I just have to wait to see if this baby is just as good as it looks like