To set the scene, I own 2 x 1Dx, 1 x 5DMK3, 1 x 1DMK4 + 2 x 5DMK2 plus a load of Canon Primes & Zooms. I also own the D800 and a few Nikkor WA Lenses purely for Underwater Photography & the 105 Macro. Prior to taking the plunge on the D800, I purchased the 14-24 f/2.8 WA Zoom, plus the Novoflex Adaptor for EOS Cameras. What the adaptor does is allows you to use the Lens on Canon EF Cameras, you retain all but the ability to auto focus, other than the Manual focus the lens works just as it would on the D800 or any other Nikon Camera.
Why would you do it ? this is simply a superb Lens, no other way to describe it, sharp with a wonderful WA zoom range that Canon just don't have, yet. Flare ? yes of course, it's a super WA lens, I own the following Canon WA lenses 14 f/2.8 L II, 15 f/2.8, 8-15 f/4L, 16-35 f/2.8 L II, 24 f/1.4 L II, 24-70 f/2.8 L II, all of these Lenses will show Lens Flare under the conditions where the front element is not shaded or you have direct sunlight entering the front element, some are worse then others, but they all have the same basic physics where light passes through Glass.
I currently mostly use the 14-24 Nikkor on my D800 for Underwater work, I still use the Lens on my Canon 5DMK3 for set landscape work where the Manual Focus isn't an issue, I'll continue to do so until Canon finally produce something in the WA Zoom that can compete on an IQ basis. Is it worth purchasing for WA work on an EOS System when you can only use Manual Focus ?, I think it is, I use the 17 TSE II & 24 TSE II and these are both Manual Focus, simply requires patience and the right set up, will I be happier when Canon produce their 14-24 ?? Yep, you bet, as long as it's as superb as the Nikkor 14-24, they're tools, not children.