There is a first review of the 28mm FE here.
It is written in an exotic language, but there are several samples pictures, including brick walls showing the sharpness in the corners and a lot of other "real life" pictures. There are also several pictures taken with the two converters. The pics were shot on an A7II and the lens may not be too bad.
Sonyalpharumors has a translation of the conclusion :
– Very sharp straight from the maximum aperture. At f/2.0 is sharp almost ont he entire frame (with very little loss on corners)
– Negligible distortion
– Very compact lens
– When using the converter EXIF data gets correctly transmitted
– close focus point could be…closer
– The fisheye converter on the 28mm lens is quite heavy
– Not really a very good bokeh (but that’s something the lens is not designed for)
Good start.. But let us see more reviews before getting too excited.