I bought a cheap used Canon lens about a year ago and I have really been surprised how great of a lens it is. Actually so much so that I have left my L series zooms at home, and have been devoted to primes ever since. One interesting piece of lore is that this lens is one of the only lenses with a curving plane of focus that Canon ever made according to Ken Rockwell. Here is an example of the quality this lens can render in tough lighting conditions.
