I don't know why people are so fussed about brigthness uniformity. As long as it's not noticeable in general viewing, I'm ok. On the other hand, focusing issue is more important, because the deskop font will immediately show the problem.
I don't think you will have any luck by exchanging to another 1070. I think every projector has uniformity issue if you measure it. Are you sure Epson or Panny are absolute uniform? I highly doubt it.
For me its visible during football games in the color of the grass. So its visible almost 90% of the time while watching sports. Sideline shots, etc.. you cant see it. I think a drop off of up to 50% is probably normal with these units. But for him his measurement dropped from 330 to 130, Which is more like a 60-70% drop.
On mine my brightest point was close to 400 with low at 115. Thats a 75% drop off to that corner... The other corners that stay at 50% or brighter are not noticeable on most content. I think these units will all have uniformity issues, the question is how bad is it on each individual unit. In talking with one Rep from BenQ he suggested that reseating the lamp could alter it slightly and change the location of the bright spot. Not sure if he had a clue what he was talking about. I didn't put much faith in his answer.