I researched the hell out of that Samyang 14mm lens; I found about 1/3rd of the reviewers screaming bloody murder about how incredible the lens is (when used properly), 1/3rd that claimed it wasn't sharp no matter what they did, and 1/3rd that claimed their copy of the lens was poorly assembled and could never be useful.
I'm still praying that my copy is in the first third, but I've only had it for a day's worth of shooting, so the jury's still out. However, I did come across The Digital Picture's comparison tool
which uses the 1Ds III, essentially a slightly older version of Canon's full-frame sensor. Their test reinforces the reports that this lens is best all around at F/5.6 (where I'm using it), or possibly one stop darker as F/8 tests pretty good and the lens does have an available stop between F/5.6 and F/8. Now I just need to get Magic Lantern running on the 6D for Focus Peeking to aid in manual focus, because using even 10x Live View isn't really accurate enough when shooting landscapes (though you can see above that I tried! Well, you will, whenever they finish uploading).
Also, holy ****, memory cards. For whatever reason, I was getting far fewer continuous shots out of the 6D with 20MP RAWs than I got out of the 60D with 18MP RAWs, even though the 60D shot 50% faster at 6FPS versus the 6D's anemic 4.5FPS (Canon is better at artificial product segmentation than Intel...).
So, I went on an SD card hunt, and wound up at SanDisk's 16GB Extreme Pro 95MB/s
SDHC card. I have the cheaper 64GB version SanDisk sells as well as an older Patriot 64GB card, and I tried a new Samsung that claimed 40MB/s writes, but none of them could give me more than seven frames on average before the camera stopped shooting for three or four seconds. Basically abysmal performance if I wanted to try and shoot any action and definitely cumbersome for panoramas that would need thirty or forty shots (layering HDR for each FOV) to build.
That SanDisk is rated for ~90MB/s writes, and I can confirm that I get 15x 20MP RAWs off before the camera slows down, and it takes less than a second to recover and start shooting again, just amazing performance. Best Buy sells these things (couldn't find them at Fry's), and they happily price match Newegg, Amazon, B&H, Adorama, etc. A big bonus if you're doing any continuous shooting and/or lots of HDR bracketing, and it may be fast enough for the RAW video stuff that the Magic Lantern team has been developing. I'll work on that at some point down the road