So I rented the Metabones adapter to try to squeeze an f-stop or more out of my Nikon 70-300 4.5-5.6 ED VR which I plan to shoot the lunar eclipse tonight. Since I'm just sitting around (with my fingers crossed hoping the cloud cover moves off) I figured I'd do an impromptu test with the 70-300 and also my Nikon 35mm 1.8 to see if thing is as good as claimed. The images without the Metabones were mounted to my OMD E-M5 with a Rayqual Nikon to M4/3 adapter. First set at 300mm with the metabones set to one click from fully open which I would guess is f4.5? You can clearly see the difference as the first shot (the wider one) is the metabones with (I think) much greater detail and beautiful contrast. This is the lens at 70mm again at one click from fully open. Again you can see much greater detail through the trees of the chapel. The contrast, again, is really very nice. This is my 35mm 1.8 again one click from fully open which I would guess at f2.0, The wider image is the Metabones adapter which shows much finer detail of the moss and beautiful contrast. So, I am impressed with the Metabones adapter. I'm not sure if it is worth $400 but I'm going to keep it under serious consideration if I plan to use my legacy lenses in the future. Good luck to everyone hoping to get an image of the moon tonight.