You are right, great tool there. I always have enough money for at least two beers in the pocket, just in case.
I went manually too until that guy came up with it. Later, I saw in the Civa forum, that others tried too but I found this one to be the best so far.

I see, the "situation save" function might alter its value here and there. But isn't it great to have such things?

As you said, the other thing is much more common: forgetting about a correctly timed change of the ADEU cards and ending up in flying circles or even worse, going back to the first waypoint of the corresponding card. What to tell the passengers?

I had those things more than once and it can happen very quickly if you have routes with short distances between waypoints.
Flights in dense airspace with many intersections following in a short distance to each other are the stressing factor here while over water would be a reason to sleep in front of the screen if ATC doesn't wake you up.  ;D

If you fly online, a "direct to" when using the INS is a real task then and then the txt files come in handy.
Maybe they clear you of some 12-15 waypoints and just give you the name of one that is far ahead.
Where is that waypoint and which card has to be loaded now? The loading itself takes some seconds too.
Of course, you could ask for an initial vector and then look that card and waypoint up, but the challenge is to be quick.

Ah, must have been a great and somehow stressful time with those big INS birds. Concorde was one until 2003 and I just found a 2006 727 picture showing the units.
Doesn't Fedex still use them?