I suspect that most people have problems with Gen Nav because it involves "sums" and most people just never do anything similar in their daily lives.
I know one friend who is about to sit the exams for the first time and he says his brain goes blank when looking at the Nav questions just because of the maths.
As with anything though, it's gets a lot easier with practice.
The instructors on my ATPL course swore by the CRP-5.
I f@%king swore by it when I had to buy one to replace my AFE ARC-1 because it came up with slightly different answers than the CRP-5
The main problem I have in using slide rule flight computers is for:
1. Private pilots. Guestimation techiques work very well for diversions whilst airborne, so why revert to an easily confused tool on the ground. During my PPL flight test we were tested on diverting using the Flight Computer to work out everything. What a complete waste of time (and dangerous if you ask me).
2. For wannabe Commercial pilots
I would like to count how many airline pilots keep their CRP-5 in their flight bag "just in case". So what's the point in learning how to use it.
That's my 2 pennies worth anyway.
FIS.