Oh no doubt! I don't see how you could hate it. I was actually thinking of renting the rarer 50mm ƒ1.0L just to play with extreme low light shots and bokeh. Although the two lenses are very similar in sharpness from what I've heard (when stopped down fast ƒ2.8).
Well its good that you researched but if you ever have any doubts theres nothing wrong with maybe selling off the 1.2 because you can buy several non-L lenses that are VERY nice. I own the 50 1.8, its sharp but I wouldn't recommend it, I gotta baby it and its very much plastic. But something like the 85 1.8 is truly an amazing lens. My point is you could get several nice prime lenses or say maybe a 70-200 with the money you spent on a prime. Generally I like to say expensive primes are for when you realized you've fallen in love with a certain focal length and/or you've got some experience at the focal length or need ultra high speed lenses. The 5D Mk.III is a great choice, some might say its a bit overkill for a new guy but I say its a rock solid investment that will last a long long time over something like a Rebel (no reason to spend money twice!) BUT prime lenses are a bit different, you do often get what you pay for but sometimes its hard to tell unless you really know what your doing. Of course it is your money but just because you can doesn't mean you should when theres other options. That said I don't think you'll be disappointed
I like to think you gotta pay to play!