I've heard that the 50mm 1.4's AF motor dies out really quickly (within 1-2 years). This is the only thing that has kept me from buying this lens.
Shhhhhhh! Don't tell my ten year old, well used 50/1.4!
Many people feel the fragility of the 50/1.4's AF mechanism (which costs about $160 US to have repaired), is mostly due to two things: hard knocks on the focus ring or front barrel, or overriding the AF manually. There are solutions for both.
Use the matching lens hood. When shooting, it nicely protects the front barrel from accidental bumps. When storing the lens with the hood reversed, it covers and protects the focus ring from getting a hard knock.
The lens is a USM model (fast, accurate focusing), but actually it's a hybrid form of USM and unlike "true" USM doesn't seem to be safe to manually override focus without first turning off AF at the switch. Some users reported doing so seems to accelerate wear and tear on the mechanisms.
My 50/1.4 has always been used with the hood and I have little reason to override it's focus manually, so maybe these are why it's had a long, happy life.
I find my 50/1.4 usable but slightly soft wide open. It sharpens up very nicely by f2 or f2.2, so I usually stop it down just a little, though if needed I'll use it wide open. AF performance is about equal to my 85/1.8.
However if you are still worried about the Canon, there is always the Sigma 50/1.4 as an alternative. They've just announced a new "Art" version will be available soon, which I'm sure will be possible to attach to the USB dock and adjust, if needed (focus calibration has been the biggest issue with Sigma lenses).
The Sigma is quite possibly sharper than the Canon wide open. But it's a little more expensive and a lot larger and heavier. It uses a ridiculously large 77mm filter (compared to 58mm on the Canon). Some like the bokeh of the Sigma a little better (it's got 9 blades, vs 8 blades in the Canon), but I personally don't see a whole lot of difference.
You need a 50mm lens for your purposes. Get the Canon or the Sigma.... and stop worrying!