8 out of 10 points and recommendedabsolute build quality, fantastic mechanical feedback, very small, exif supportedsharpenss is not so great, design of rings are not pragmatic
The lens is the piece of jewery in terms of beauty, build quality, mechanical feedback. I've never used as smooth as this lens' focus ring. It's butter-smooth, you can rotate it with one finger without any struggle. Aperture ring's feeling also very good. It's small but not light. It doesn't feel any cheap.reviewed May 24th, 2015 (purchased for $950)
One of its weakness is its sharpness. It's not sharp as Sony FE55.8ZA, not just center but across frame. It's Planar design so it should be expected that Sonnar design(FE55.8ZA) would be better at it. but I expected more even sharpness than this. Center sharpness is very good but not at border. Maybe not a big deal for Planar fans.
Also rings are very pleasant to use but it's not designed well in terms of pragmatism. There's no diamater difference across whole lens. while it makes lens look sleek, it's not good to actual use. You should find yourself rotating rings not intented way when you're trying to mount it or unmount it. That can't be good experience consider this is very expensive lense. I think 50.4ZF/ZF Planar's exterior design is much better to use.
Still, if you prefer mechanical feeling, premium build quality than absolute sharpness(I won't say it's bad. actually it's quite good. Just FE55.8ZA is better at it.), This would be worth it.