Great lens, especially for the price. Indeed, it seems to be as good as the Canon 14mm 2.8 II and better than version I.
I process my photos in Lightroom and the profile I downloaded through the Profile downloader is good, but I found a better one I have yet to install manually. The existing profile corrects the wavy distortion fine and also the vignetting. There is no chromatic aberation to speak of. The profle is efficient, in that it crops very little of the image.
Here are a couple of photos. The first is on a 5D MkII 30 seconds at f2.8 at ISO 3200.
The second is at 1/40 at f8 ISO 100.
If gear matters: 6D, M3, Samyang 14/2.8, EF 24-105/4, EF 35/2.0IS, EF 50/2.5 macro, EF 85/1.8, EF 200/2.8II, EF 400/5.6, EF-M 11-22/4-5.6, EF-M 18-55/3.5-5.6, EF-M 55-200/4.5-6.3, Ext 1.4x, Lifesize conv, Ext tube EF25, 430EXII, 270EX, Yongnuo 603C