I received my R3A / 40/1.4 combo just before Christmas. Not having had the chance to really take it out in the meantime, I just took a few shots on the go.
On a shoestring:
The 40 seems to have a stunningly strong resolution capability. I have uploaded an example to my gallery which evidences that ("Resolution"). I couldn't want more resolution - this is as much as I can draw a benefit from. Stopped down, the 40 Nokton is incredibly strong, I think.
On the flipside, used wide open, the 40 at 1.4 and, to a lesser degree, at 2 has an unpleasant out-of-focus area rendition. It almost looks like a halo-effect, and can be irritating. My Zeiss lenses for the G don't do that. Example: "Out-of-focus area".
Then there's another rather weak point: Vignetting wide open under low-light conditions. The Nokton used wide open seems to do that more than any other lens between 35 and 50 focal length that I use. It does worse than the Nikkor 35 1.4, which, at 1.4, is not impressive in this respect. By the way: My new R3A/Nokton had a very strong impact on my 3-year old daughter. She insisted to have a new camera as well, so I had to tinker one for her. Examples o fresults are also uploaded to my gallery ("Vignetting; Handicraft").
I should say though: The above downsides don't disqualify the 40 Nokton at all, in my view. This little lens can do great things when one is aware of its limits. And even if the limitats shold hit - who cares really. A bit of vignetting will never kill a strong image!
The R3A handles intuitively in my hands, I like everything about the ergonomics. What's not for me is the finder. Wearing glasses, and having used with manual Nikon SLR for a very long long time, I'm used to move my eye around when framing. But the 40 mm frames are too far out for me. They give me a hard time getting a sense of proportions within the frame. I don't think I'm going to get used to it. As a consequence, I have an R2A with a 35 Ultron on order. I checked with an R2 before, and it works fine for me.
Without glasses, the R3A finder is
fantastic!
Here are the examples:
My gallery.
Cheers, Gerold