I wonder how well it performs at close range. Most unit-focusing lenses are optimised for infinity or far distances, and the near focus distance is limited at the point where optical performance starts to drop off (usually a little less than 10x focal length). Indeed, the older 40mm Ultron focuses to 0.38m, but it comes a dedicated close-up lens to reduce the focus distance to 0.25m. If the the close-up lens is well matched to the lens it could provide improved image quality at close range, compared to increasing magnification purely by extension.
Now the new version focuses to 0.25m without a close-up lens, and the optical design appears unchanged, so we might expect some drop in performance at very close range. On the other hand, sharpness near the center of the image usually remains fairly good, the corners suffer more, and close-ups are often of subjects like flowers which are placed centrally and corners are not in focus anyway. Also, closeups are usually shot stopped down which improves performance, so maybe this is a good compromise. Continuous focusing to close range is certainly far more convenient than fiddling with close-up lenses.
The new lens is not as compact as older versions, but is still very small compared to most other similar lenses such as the AFS 35/1.8 or AFS 50/1.8. It is about the same size, but heavier than the AFD 50/1.8.
I love the classic styling of this lens, and with a modern optical design, CPU, useful focal length and speed, compact design with close focusing, it is a very appealing package... The question is, do I really need another standard lens??