Topically, hexadecimal is extremely useful for programmers to understand, and makes binary in general quite a bit easier to work with and represent both in code and out.
Though not as important as understanding binary in general, looking at some simple math in binary will allow you to conceptualize some of the operations that you will be working with on a regular basis.
After a couple week delay all of my apps are back up on the iTunes App Store. Thats right, not just Statistical Free. As it turns out when they say "Bank Pending", they mean, "go into contracts and view/submit them all again."
I personally believe that a basic, if not strong, understanding of the binary (or base 2) counting is crucial to understanding how computers work. And, thus, to being a good programmer.