It's almost shockingly heavy. Noticeably heavier than the 50 Noct. And somewhat larger (mostly longer) as well.
    Of course the craftsmanship is world class. The twist-out lens hood, like the 50 APO, is a joy to use. In contrast, I find the fidgety 50 Noct telescoping hood to be less reliable and less fun to use.
    The outer (white) box contains an inner (silver) box which contains FOUR smaller cases/boxes: 1) the usual leather lens cylindrical pouch; 2) a leather pouch for the tripod shoe (!); 3) a regular plastic pinch-to-use lens cap; 4) the second inner box (black), secured with the ribbon envelope-style clasp, containing the 75 Noct and a lovely black metal cap that covers the entire outside rim of the lens. The lens is bagged and in a black satin-covered contoured foam clamshell affixed inside the second inner black box.
    The RF calibration was very good when used with my M10.
    Wide open, I was surprised to see evidence of a bit of camera shake shooting at 1/90 or even faster when fully zoomed into a photo. I don't usually see camera shake when I shoot the 90 APO on the M10 at 1/90. Perhaps part of the reason for more apparent shake with the 75 Noct is...
    Wide open, this lens is astoundingly sharp. Even though the MTF curves suggest it is not sharper than the 50 APO, the images convey the sense of being even sharper than the 50 APO perhaps due to the longer focal length, small MFD for a Noctilux, and magnification factor. Remarkably, the sharpness does not fade as you approach the edges of the image (the drop off in sharpness away from the center is very apparent with the 50 Noct, by comparison).
    Wide open, the lens is astounding contrasty. In this regard, it reminds me very much of the 50 APO, except at f/1.25.
    Wide open, the lens has far less CA than the 50 Noct, but not as low CA as the 50 APO. Still, for a f/1.25 lens to show such control over CA looks almost... disorienting to me, not unlike the first time I shot Zeiss Otus wide open.
    The bokeh and the fall off between in-focus and out-of-focus regions of the image is simply lovely. The bokeh is less prone to be colored by CA, and is smoother-looking overall in my opinion, than that of the 50 Noct. And I think the 50 Noct offers very nice bokeh indeed.
    There was some curious debate about this issue in a another thread, but I can confirm that in a few real-life portraits and test shots so far, it's clear that even "in use", the depth of focus is often indeed thinner than that of the 50 noct. (In other breaking news, numbers are still the best way to determine which of two official depth of focus ranges is larger...)
    My hit rate shooting the 75 noct wide open with the RF on the M10 (maybe 50% sharp focus, 70% ok focus or better) was not as bad as I thought it would be off the bat. I found the focusing accuracy to be no worse than, and possibly better than, the 50 noct despite the thinner depth of focus at the MFD, perhaps because it's just substantially sharper to begin with, especially away from the center, so a bit of focusing inaccuracy can still lead to a reasonably sharp capture, at least by the standards of the 50 noct.
    My hit rate shooting the 75 wide open with live view was very high, in part because the lens is so sharp and contrasty that the focus peaking is very apparent. In contrast, the 50 noct shot wide open away from the center can be soft enough that focus peaking doesn't light up much.
    The 75 noct does not swallow nearly as much light wide open as the 50 noct wide open. Which again, math will tell you (50@ f/0.95 vs. 75@ f/1.25), but what this means to me is that I am keeping both the 50 noct and the 75 noct, because they have different niches. When light is an extreme premium, or there is a need to shoot at a low ISO, the 50 noct will likely be more useful than the 75. The 50 noct is also noticeably "dreamier" in its rendering than the 75 noct. I'm sure people will debate the usual "Leica glow" vs optical imperfection vs atmospheric vs clinical rendering... but it's safe to say the two nocts draw the same subject quite differently.