I tend to use some proprietary scientific software, but a lot of it is because academia already has already invested in codebases for, say, Stata, GAMS, Matlab and so on. But Matlab is two steps removed from raw Fortran; and what sets it apart from the many identical-syntax clones are a few narrowly-oriented toolsets aimed at some kinds of engineers.
Mathematica is the only one I buy versions for my home computer. It's very, very good.