Navbox Pro is great, for VFR and UK-style IFR (on the IMC Rating) type of flying.
It should be standard issue in PPL training; the slide rule should be ditched. Think of how many pointless training hours would be saved; they could be put towards better (post-WW2) stuff.
For IFR/airways, one needs something that supports airway routes with a lot less effort; Jeppesen Flitestar IFR is the only option for Europe.