I am very annoyed from the deviations even on relative short routes. I read through the posts and could not find a single argument favouring rhumb lines, also in this reply. I could also comment in detail:
"This has been discussed at length in these forums before, and equally good arguments put forward for rhumb lines - the primary one being that SkyDemon is a VFR-only tool aimed primarily at pilots of SEP aircraft and helicopters flying relatively short routes."
So it shouldn't matter to them, because they don't note a difference. Rhumb line or great circle is not flight rule dependent, I prefer to fly a great circle as well flying VFR, also my built in GPS doesn't note the difference in flight rules.
"A rhumb line is defined by a single heading which is close to the heading a PPL will measure from a Lambert Conic Conformal chart (if they remember to use the middle of the line!!!) whereas a great circle route has a constantly changing heading and is an unnecessary complication for most of the pilots Skydemon is aimed at. "
Also on a rumb line the heading is constantly changing (even the true one) because the wind will change along the route. Actually the course is constant for a rhumb line. And as already mentioned, there is no complication because people flying only VERY short distances will not notice it all, whilst people flying only moderate distances in order 100s NM east/west direction at out latitudes will be annoyed by rhumb lines and not by great circles.
"Previous discussions here have suggested that the choice of rhumb line vs great circle should be a configuration option in SkyDemon, although the default must be rhumb lines for consistency with the current interface."
I even see no point for a configuration option because great circle would make everybody happy. For the PLOG I would not care to leave it as it is, the mean course and heading would be fine. Of course configuration would be nice to show the differences in lessons.
"Incidentally, a straight line on a Lambert Conic Conformal projection is not
actually a great circle route, although it is a good approximation for short routes."
The great circle is a very good approximation compared with the rhumb line, you will use charts where the cone constant represents approximately the earth's convergency. So why using a rhumb line that is a much worse approximation when you can have the better great circle?
" The error between a rhumb line and a great circle route is also insignificant within the DOC of most radio nav beacons, again because of the short distances involved."
Why do you want to be inaccurate when you can be accurate?
The last points you mentioned I can summarise you also think great circle is better but you accept the inaccuracy. I wouldn't if I had the choice. I really see no complication at all for a user not understanding the difference, the opposite: They will not be surprised that the built in GPS shows a different route.