The latest builds works great for me, 5D3.123 with external monitor, using MLV - before I had skipped frames from time to time at 1080p25 with Komputerbay 64GB, now I filled three cards without any skipped frames. The image in the EVF is much more usable with mirroring on. Just wished there was something to give me confidence that I am acutally recording when I am only looking through the EVF.