Three reason I love the Sony FE 135 F1.8 GM 

Bokeh Master. Subjects appear 3D...Need I say more!!!

Easily the sharpest Sony lens

I previously owned the Sony FE 90mm F2.8 G macro. At the time I thought that Sony wouldn't be able to match the quality of that lens. The Sony FE 135 F1.8 GM thus far has the best image quality. They really outdid themselves with this one.

Focus Speed

Not only is the Sony FE 135 F1.8 GM lens sharp but it's fastest lens that I have used when it comes to focus. When you pair with the Sony A7Riv and the Sony FE 135 F1.8 GM,  I rarely miss focus even when at aperture f1.8.