I have a PhD in theoretical atomic physics and teach physics and astronomy near Chicago. Mathematica was indispensable when I was debugging my FORTRAN code for my dissertation, I still remember the day I found that nasty bug! Anyway, teaching takes most of my time now and the "research" I now do is trying to understand Mathematica more fully. I use it in most of my classes and I'm in the process of developing interactive simulations specific to the topics in the courses I teach.