Rokinon 14mm f/2.8 is a full manual lens that you have to stop down to figure out the exposure.
Which again dims the viewfinder and you cannot really tell what is in focus and what is not.
The distortion is quite shocking as well. It is cheap, OK. I have it and I am still climbing the learning curve. I am not sure if I 'll keep it.
Rokinon is easy. Dial in F8, focus at 1m (3ft) and you're set. (Hyperfocal is <1 meter) No need to be able to tell if something is in focus or not, because everything will be.
For distortion, there's LR profile you can use. It doesn't make it great, but it helps. For the price, it's amazing lens.
It seems that the new 16-35 f/4 IS is optically superior to the f/2.8 lens. The IS gives you two apertures that can help you get your shot –unless the subject is moving, of course. Do you actually buy lenses because they are 'cool' or was that a joke?
Anyone who considers himself (/herself) a photographer, should only buy 2.8 or faster. You can easily spot the amateurs carrying the F4s around.