The EVF on the NEX-6 is essentially the same as the external one for the 5N/5R/F3. Very high resolution and eminently usable, particularly when using manual focus lenses. Now that it's built into the body of the NEX-6, it's even better.
Though the peeking function has been a blessing for using very long lenses on the NEX camera, it's unfortunately not precise enough when depth of field is thin. Focus fine tuning is still required and I almost always do, and do it with MF Assist feature, which enlarges (zooms in) the area of focus. On the 5/5N, this was an awkward thing to do, as the MF Assist is button "C" at the bottom. Engaging it means shifting your thumb down. On the NEX-6, the AEL button can be reprogrammed to MF Assist. This button is much closer to the thumb and it takes no efforts at all to engage it.
The changes above have made using manual focus lenses a lot easier. One feature I wish Sony would add as a firmware update, is to allow the wheel under the mode dial to be programmed as exposure compensation if an auto focus lens is not detected.
Overall, I am very impressed with the NEX-6. It's by far the best NEX camera Sony has made. I like it even more than the flagship NEX-7. Well done, Sony.
Waiting for the bus - NEX-6 & Jupiter-9 85mm f2.