One of my favourite lenses of those I've owned, sold to make way for a 70-200 f2.8L, which I need for video.
No regrets but I enjoyed this lens whilst I had it, found it to be a terrifically fast performer, especially with the focus limiter set. I also struggled with the hood. It slackens off over time.
I found it a very fast lens in use, when I'm shooting stills with the zoom I tend to play about more during my shot, with the fixed 200 it was a case of point and blast. It made me more decisive in that way that primes by their nature do.
This lens let me track a jet ski coming directly towards the camera in AiServo on a basic Rebel XTi. Every shot in the sequence was optically usable. A brilliant lens.