I’ve had one of these for a couple weeks now. It’s a <$400 Korean made lens that's sold under a bunch of different brands (Rokinon, Vivitar etc). Mine is all manual but they make a somewhat pricier version with a metering chip, at least for Nikon mount. None of them have autofocus though.
It’s mostly metal, apart from the built-in hood, and seems pretty solildly put together, but the cap is kind of fiddly and annoying (it has to be aligned to lock in place)
I have to say I’m quite impressed with it optically, it kicks the ass of my other ultra-ultrawide Sigma 15-30mm by quite a margin, especially in the corners. On the minus side, vignetting wide open is pretty extreme and there is some complex barrel distortion (PTLens corrects it OK, but you lose some wideness correcting it). But I think the only better option this wide (for Nikon at any rate) is the 5x pricier 14-24.
It seems like kind of a no brainer for the price on a full frame/35mm system, but I’m not sure if it makes as much sense for small sensor DSLRs. On the other hand, 14mm is going to be distinctly wider than an 18mm kit lens, and the vignetting won’t be nearly such an issue.