After taking the glass out of the box I noticed how light and small it is in terms of medium format. The build quality is like the 63mm. After screwing it on my GFX50R the lens was ready to shoot.
The first thing I noticed is a constant light buzzing noise coming from the lens when the camera is on shooting mode. I've asked Olaf Stzaba who owns the same lens and his lens is behaving the same. The 63mm is totally quiet. I guess it has to do with the linear motor drive inside.
With an maximum aperture of 3.5 it this lens can't be considered as a fast lens. For normal street photography at daylight it is fast enough. The image quality is flawless and there are no visible distortions and vignetting (autom. corrected in software anyway).
For around 500 bucks this lens is a real bargain. Go and get it. It is a solid companion with great image quality. Keep an eye on Fuji. Many lenses go on sale from to time to time.