I always thought of HSAB (Hard/Soft Acid Base) as being more of a conceptual aid rather than an empirical tool. It is my opinion that HSAB can be useful for developing a better conceptual understanding, but it's not reflective of reality and therefore is very limited in it's practical application. You can't easily express HSAB in a quantitative form, unlike thermodynamic/kinetic relationships.
But these are just my opinions.