Bought mine ~ 5 years ago - used. I do not know how long it was used before.
After ~3 years it have sometimes not working AF - suppose that is starting AF problems. Since then I have a hood - before that I have not realized that this lens needs a hood for a longer live of the AF.
Since ~ 2 years I use manily manual lenses like the Minolta Rokkor 58/1.2 instead of the EF 50/1.4.
Mine survived a 5 foot drop to concrete. That puppy bounced, but had no issues. I think the claims of the lens breaking are an issue of the vocal minority.
ive had mine for about a year now, not too impressed tho, im finding it not to be very sharp on my 7D but theres a good chance it might just be the calibration not the glass, focus ring is not as smooth as i would like it to be but its not bad. as for going with sigma, i have not experience with them yet, but i have heard good things.
Funny thread to see, since I just dropped mine on cement today (3'). Then it bounced down some wooden steps and settled underneath one (neither cap was on as it wasn't locked into the camera). Never had that feeling before and hope to never have it again - My own dumb fault. After bringing it inside, a quick prayer and a good cleaning - it's barely scratched and still shooting great! Had it about 4 years I think and I Love the lens! My first thought was 'do I have enough in the camera kitty to replace it?', fortunately it didn't come to that, and I'll be able to shoot my son and his date in their prom tux and dress with it tonight!