(Context: Lens released 1993, I used it for about 8 years, shot a LOT of photos with it. Like most of my Canon lenses, I have now sold it. Review written 2017)
I used this lens A LOT until I started looking at my photos more closely and deciding I wanted more sharpness. I mostly used this lens at f1.4 at first, and later started using f1.8 to f3.2 more often to get better sharpness of the subject. At f1.4, though usable and printable at small sizes, it is certainly not perfect image quality. Stopping down to f2 helps a lot and f3.2 helps more. From the front, this lens has such a classic look that it is used in a lot of Canon’s marketing images for their cameras. I sold this lens because I had actually taken TOO MANY photos with this one lens – it was time to try a different focal length. These days there are better 50mm lenses out there – though they are much more expensive than this one: the Sigma 50mm 1.4 Art; and the Canon 50mm f1.2L USM. If only the Canon 1.2L had image stabilization, it would be almost the perfect lens. There is also the smaller, cheaper, new 50mm f1.8 STM which is pretty good. (2018 Update: Canon now makes an 85mm f1.4 with image stabilization - will that be brought across to the 50mm? I don't know, but if they do update this 1993 lens with image stabilization, and make it an L series, the price will be at least doubled for sure!)
Compared to other lenses
I have also used the 1.8 II, and I certainly prefer the 1.4 – mainly because the focus ring is much more useable. Speaking of which, the focus ring on the 1.4 is just ok. It has the usual small-rotation-makes-large-focus-change as per all Canon SLR lenses I have used. And there was some play I the ring – at least in the copy I had. I would prefer a slightly more accurate focus ring. I have not used the Sigma 50mm f1.4 Art lens but my understanding is that it is miles better than the Canon in most ways. There are also wickedly good Ziess 50 or 55 mm lenses, but with Canon mount, they are manual focus only and REALLY expensive. I haven't used the new 50mm f1.8 STM but it is likely comparable in image quality and costs less.
The Canon 50mm 1.4 does not focus as fast or accurately as the L-series lenses I have used – focus is loud and jerky but not as bad as on the 1.8 and 1.8 II. Based on my experience with the Sigma 35mm, I wouldn’t expect the autofocus on the Sigma 50mm to be any faster than the Canon. You might end up switching to manual focus - and the focus ring on the Sigma lenses is better than on the Canon 1.4.
In summary, do I recommend this lens? Depends: if the only lens you have is the kit zoom lens that came with your camera – the Canon 50mm 1.4 USM is much better than the lens you have, and you should get it. If you can’t afford it, you should get the 50mm f1.8 II - or newer 50mm f1.8 STM - which is also much better than your kit zoom. If you want 50mm and you can afford to get the Sigma, I would get the Sigma over this Canon. If you are a professional portrait shooter you already know the answer: the Canon 50mm f1.2L USM… or get an 85mm if you have a large studio. Having said that about the 1.2L, some people don't love the 1.2L whereas I have never heard a complaint about the Sigma Art... just a side note.