ePhotozine reviewed the new Samyang AF 45mm f/1.8 FE lens and concludes:
With a high level of performance and a pleasing character, the Samyang AF 45mm f/1.8 FE lens has plenty of potential to become a favourite. There are some parameters that may need some additional correction in software, not really an issue as the solutions are there. It is light and compact and generally just delivers the goods in a simple, discrete package. When used for street photography, it can be an advantage to use an unobtrusive lens.
There is some flare and there is no weather sealing, so these are a couple of disadvantages, but to be absolutely fair, the price tag is a very attractive one and generally, the Samyang AF 45mm f/1.8 FE lens is a delight to use. Highly recommended.
Marc Alhadeff posted an even way more detailed review:
Everything is not perfect but the lens scores very well on all the main points : very good to excellent sharpness, very good color rendition, beautiful blurry background , good bokeh balls wide open, efficient AF, small/light/cheap on a full frame mirrorless
Allan Weitz also tested the lens and writes:
If you’re looking for an extremely small and extremely lightweight wide-aperture normal lens that is a piece of cake to tote around all day and won’t break your wallet, by all means take a closer look at this lens.
Samyang AF 45mm F1.8: First Look | 4K