I don't have the Rokinon 14mm, but have used several Rokinon lenses and been impressed by them. All have seemed well built and very nice optics. I've still got a 21mm f/1.4 Rokinon for use on an APS-C mirrorless camera. It has a somewhat "old school, good solid metal & glass" feel, along with smooth focus and solid aperture clicks (half and full stops). The only glitch with it has been that the plastic hood no longer "clicks" to keep it securely in place, but I have a metal screw-in hood that works fine on it (no concerns with the 14mm lenses, as they all appear to have permanent, built-in hoods).
You didn't mention what camera you want to use it on, but I believe you shoot with Nikon...
They've sold under at least four different brand name. As Jerry said, they besides Rokinon and Samyang (same company), there were early versions selling under the Bower brand. Also there were ProOptic, which was (still is?) Adorama's house brand. I think the Bower and ProOptic were only the first version. Most versions have a large diameter, convex front element and a built-in lens hood. As a result, most versions cannot be fitted with screw-in filters and require a special lens cap (might not be able to replace the cap if wasn't included with a used lens or is later lost). Most versions (unless noted otherwise below) are manual focus and manual aperture.
There have been several versions of the 14mm, although not in all mounts.
- First version (sold both as Samyang and Rokinon, but also sold as Bower and ProOptic).
- "Chipped" first version, which allows partial EXIF data recording and allows the camera focus assist, auto exposure, auto WB to work.
- "SP" version seems to be similar to first optically, but with a redesigned barrel. It looks a lot like the IRIX 15mm, in fact. It has a faster f/2.4 aperture that apparently can be controlled by the camera (not manual).
- "Series II" version appears to be more compact and have some other functions I am unfamiliar with.
- "AF" version is now being offered under Rokinon and Samyang brand names. As far as I know, these are the only ones with autofocus.
I seem to recall there were some issues with decentered elements in the very earliest version. Images made with those lenses would be "soft" on one side or the other.... wouldn't focus evenly across the whole image. It probably was due to poor quality control during assembly. Some people were very happy with the lens they got, while others would have to buy, test and exchange one or more times until they got a "good copy". It's something to watch out for, if buying a used copy of that first lens. The problem may have been fixed in the later versions... at least I don't recall hearing anything about it since when the lens was first introduced
I did a 14mm lens for Nikon F-mount search at B&H and was surprised to see pretty much all versions of the lenses still being offered (as well as some brands)!
https://www.bhphotovideo.com/c/search?q=14mm%20%20&filters=fct_lens-mount_3442%3Anikon-fMy favorite reviewer at The-Digital-Picture website apparently hasn't reviewed any of the Rokinon/Samyang 14mm lenses.
Ken Rockwell has done a review of the first version (refers to it as the Samyang, even though he got the ProOptic branded lens).
https://www.kenrockwell.com/tech/samyang/14mm-f28.htmI recommend you search further online for written or video reviews of the specific version of the lens you're considering.