I think it's almost essential for a physics student to have at least a basic understanding of general chemistry. The amount of overlap between physics and chemistry is pretty huge in many areas, and seeing the material from the perspective of chemistry can be beneficial in physics, even if only due to providing a wider perspective of a given phenomenon. I'm in physics III and we're covering atomic and nuclear physics currently. Having seen at least some of this material in chemistry has made learning the material in physics much easier.
Usefulness and relevancy aside, I simply think that it's important for any science major to have at least some familiarity with the major areas of science. My knowledge of biology is fairly limited, but I'm glad I have the knowledge of it that I have. Topics relating to biology only rarely come up in physics, but they do come up. Even if only in tangential ways. A cursory understanding of the human eye (the eye in general) is helpful when studying optics. A basic understanding of our anatomy and physiology is helpful because we can see things like the simple harmonic motion of our "default" walking pace or the fact that the human body is a heat engine. It's not necessarily essential to understand the biology or the chemistry behind the various topics that have connections to topics in physics, but in my opinion it's very beneficial because it allows one to form a more complete picture of many topics.
And this goes both ways. I think it's important for biology and chemistry majors to have a basic understanding of physics as well.
edit - I've met several biology and chemistry majors that seemed to disagree with me on that last point...lol