Not for the faint-hearted, but wonderful when mastered.
The 85mm market is crowded with Canon. Canon has their 85mm f/1.8 (excellent quality and value!), their uber-expensive f/1.2, as well as Sigma f/1.4 models from Sigma, Samyang and Zeiss. Between the Canon's is the Sigma with a fair price and the Samyang appeals to the budget market due to its manual aperture and focus ring (no electronics).
The Zeiss sits between the Canon 1.2 and the Sigma in terms of price, which is weird because it is manual focus only. It also has the oldest and most simple design of the lot. But for the money, it is a beautiful looking lens and very solid. There is no plastic or rubber, it's all metal and glass.
This is a lens for two purposes. At long distances, it is quite sharp, very contrasty and when stopped down, very sharp - perfect for a compressed landscape. Up close, it maintains the contrast, but the finer details soften, allowing a soft, flattering portrait. I like both looks.
But there is a catch. The very same design that allows these two looks to exist is the same reason why this lens is so difficult. The portrait's softness comes from spherical aberration, where the outer portion of the lens focuses at a different point than the centre, retaining detail but softening any harshness. However, as you close up the aperture, the focus point shifts quite significantly. So shooting a portrait at f/2.8 or f/4 will often give sharp ears, rather than sharp eyes. This is why you need to master the lens by knowing its quirks...
To get around this, i often shoot portraits at f/1.4 utilising my camera's AF assist (focusing from infinity and then rotating to MFD gives me better focus accuracy than MFD toward infinity). For shots further than 5-7 meters away, I tend to use live view. If I want to stop down, I just use live view with DOF preview for best results. I have a focus screen on order with a split prism that will hopefully allow easier viewfinder focusing but I haven't received it yet.
So what's my summary of this lens? Wonderful at both portraits and landscapes... However the reason it's so good at both is the reason why it's so hard to use. At f/1.4, the depth of field is tiny, so correct focus is a must. At f/2.8, you have slightly more depth of field, but the focus shift is even greater. You really need to learn the behaviour of this lens to appreciate it. As such, I would never recommend it to my friends, even those who are photographers unless they were fully aware of it's behaviour.
For certain, you'll miss shots and it'll let you down... But the shots you get will flatter you and make your subject gasp.