I still enjoy using my flight computer. I used to struggle, but I can generally out-calculate someone on a calculator. Also, it's easier to recognized "input crud, output crud", as the figures are there in front of you.
For tests such as the navigation, you will need it. A simple scientific calculator is always useful too, especially when working out moment arms.
Anyway, back to topic. I find most people ditch their CRP or ARC after they pass, and they seem to do fine.