I hired a 50 1.2L for yesterday's wedding shoot, as I am strongly considering changing from a zoom based setup to using mainly primes. 50's a focal length I like so that's where I thought I'd start.
I'm very impressed with what I see for the results - very versatile and a gorgeous look that simply isn't possible to document - have to just use one, and I'm glad I now have! Getting the shots in low light, however, was a right PITA. Focus is somewhat sporadic, and quite slow. If that's the best there is, then OK, but it wasn't very assured and meant I was more pessimistic about the results than I am now, having looked at the shots.
I am also considering a second FF body to help with the problem of having the wrong lens - with Canon that's another 5D3 - owch!
So... people who know - is Nikon's 58mm as much of a pain to shoot as the Canon 50? I've seen results online which look pretty similar, so it's more the actual use of it I'm interested in at this point. ta muchly

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The initial Canon lens I bought was a dog so I have a replacement which appears to deliver in all my test shots, so sharpness is now there. What I have noticed, and what your shots look like they back up, is that the Sigma does deliver a warmer image. I can fix it in post for the most part, but the colour and contrast I must give to the Sigma.
And Canon really needs to bin the old 50mm 1.4 and replace it with something better IMHO!
Apart from catching flu from the bride, who was sick as a dog, a largely successful and educational experience.
My second Canon 50 is a fabulous lens. It is pretty sharp even at 1.2, but at 1.4 I really can't fault it. Delivers much, much lower levels of CA, and AF hit nearly every time. Fabulous images, used it for the Group shots as they are small groups, and the look is wonderful.
135 was also a success, really good for candid shots, especially before people have had a few drinks - that point in the day where a photographer is not what you want near you. Hanging back with a small black lens allowed me to get some good shots, and f2 loses the background really well.
The Sigma 24mm was less impressive, however. Focus was all over the place, especially nearer infinity. When it nailed it, I was impressed. Colour, contrast and sharpness were good. Only trouble was of nigh-on 300 shots with it, I think I kept < 50.
Reading up, I see I am not the only one. I have returned that lens, and now I need to mull what I do next. Mostly, I used it on my 7D2 as a pairing with the 135, with my lead shooter using an 85mm. That means most of my shots are more like 35mm, which is a focal length I've never really used. Seems I might like it, so that has opened a big can of worms as to what I do next...!