Wow, I've been working on network protocols and performance for nearly 20 years, and I've only encountered a little calculus in a handful of research papers. It's never been necessary for my work. In fact, I have a hard time imagining the kind of work that would require calculus.
Numerical analysis? Sure, but you'd probably want to bulk up on the math for that kind of work anyway.
I was required to take three semesters of calculus for my CS degree. I think that any educated person should have a basic understanding of calculus, so one of those was not a waste, but I sure wish that I'd spent those two extra semesters learning more graph theory or computability or information theory or just statistics, any of which could've come in handy. As it is, meh.