I have been Voxengo user for many years and appreciate the products very much. I daily use the GlissEQ, SPAN Plus, Elephant and MSED in my mastering, other products like the Soniformer I use for particularly tough problems. The great thing about the Voxengo products is the possibility to adjust them very precisely to your needs.
The GlissEQ is such a powerful plugin, if you take the effort to make some presets your starting point. So, I usually use it 2 times on a mix, once for notching (often dynamic), once for m/s EQing.
The SPAN Plus is an excellent analyzer, which also allows a comparison before/after by several routing possibilities. Elephant has been one of my favorites for years, because it can be adjusted very precisely and, in contrast to many other limiters, doesn't lose the bass so quickly and has less of a tendency to hardness than most of the competitors. In addition, there is the stepless scalability of the GUI and the resource-saving programming, which scores unequalled.