fixed focal length

This is my current favorite lens and the one that resides most often upon my camera. It certainly is the sharpest lens that I own. I use it for ordinary photography as well as for macro photography. As I shoot plant life with the macro capability, I don't mind the short working distance (distance from front element of the lens to subject, about 2 inches), as the plants don't run away when you close in on them. If you want to shoot bugs, etc, you probably want a longer focal length macro (longer focal length=larger working distance). The lens is capable of life-size reproductions without accessories, a definite plus over the Canon made 50mm macro lens.
This lens makes a great general purpose normal lens, as the very high optical quality for the macro uses leads to excellent sharpness and freedom from abberations at distance. The only drawback to the lens is its rather slow (for a 50mm prime lens) maximum aperature of F/2.8. As I usually shoot in sunlight or with high-speed films (or both!), this has never been a problem for me, but others may prefer a faster maximum aperature.
I've shot with this lens with all its aperatures from wide open to F/45 and found, in my subjective eyeball test (I look at prints and slides), that the optical performance varries very little over the aperature range, being uniformly excellent.
Overall, a fine lens for an even finer price.

I shot the illustrations for an antique price guide with this lens and got compliments on the slides from the publisher, so it definitely gives proffesional quality results. These days I prefer working with a longer macro lens, so you can get a little more working distance between you and the subject, but that is a matter of taste, and the longer lenses cost more.