I had a brief love affair with the 50L but sold it.
I now have the 24-70 F/2.8 II and the 70-200 F/2.8 II.
All the primes have been sold because, in my opinion, they are not good enough for the latest Canon bodies.
They are either too soft or have focusing issues.
The 50L is soft as butter, smooth and has creamy bokeh.
Sharp it is not.
Not even at F/4 - F/8.
Sharp is the new Sigma 35mm F/1.4 or the 24-70 F/2.8 II.
If you want to know what a real sharp 50mm is, try a Leica Summicron
Anyway, the 50L is a fun lens but it renders completely differently from the zooms.
It's a pig to get accurate focus @ F/1.2, but if you buy a 1.2, I'd assume you'd want to shoot it at this.
It can take a lot of work to get good consistent shots out of it.
It's also a heavy pig on the 5D MK3 and doesn't really balance well on it unless you use the grip.
I sold mine and don't miss it.
You can always soften a sharp lens in post but you can never sharpen a soft lens...