I am resurrecting this thread because I received my Proscreen for the D3 the other day. I don't know how to put this politely, but I was not impressed. I have a brightscreen for the Leica R9, and that worked brilliantly, but the one I got for the D3 worked quite poorly for me. It was dimmer than the stock screen, and while the big 13mm microprism center area with split rangefinder was helpful at times, I find it too intrusive to the view in the camera. It focused accurately, but I found that even manual focus was easier using the stock screen. I thought I just put it in wrong or something the first time, but I took it out and in several times, all with the same results. In comparison to the R9, using an f/2 lens with the brightscreen was far dimmer and more difficult to focus than the R9 with a f/2.8 lens. I totally wanted to love this, but it was a huge letdown. Even if it were free, I would not choose to have it replace the stock screen, yet it was 200 dollars. So back it goes. I will either get a refund or exchange it for the magnifier.
I was debating whether to post this, but I just wanted to offer another opinion. I am also completely willing to concede that the screen itself might be defective in some way, but given that it did focus accurately in both AF and MF when it was in, I think it had to have been in correctly. Also, there is pretty much only one way those screens will fit in...