It´s a fun lens. My copy is great. I use it quite a bit stopped down to get best results and a huge DoF. That way the focusing is less critical.
The distortion is rahter hefty and it can cause problems like in the first of my photos. In most cases it is not an issue for my usage.
Sure, if the Canon 14 L was only twice as expensive as the Samyang, I would probably get the Canon but right now there is absolutely no reason for me to invest in the L. I´m awaiting the rumored superultrawidezoom however, that will be interesting (and probably too expensive the first and second year).
I like most of those shots, but you should have tried to correct the mustache distortion in the top image. The tree is a great compostion, but I would have fiddled with the green palette to make it more varied. Not trying to nitpick though!
I am wanting to shoot Milky Way images, besides daytime use. So I would prefer if it doesn't have much CA and is reasonably sharp, at least to the borders, if not the corners...and at least by f/3.5, if not wide open.
If it is only acceptable by f/5.6 or 6.3 at the borders, that wouldn't be good for 45 seconds or shorter night exposures...because ISO would be pushed from 3200 to 10,000 or higher...