"Nathan Young"
Thanks, a good reminder that even though the plane is IFR equipped,
the pilot may not be ready to use those instruments. I guess there's
something to be said for the simplistic KX-155

Is there a broader question of whether any pilot is fully capable of
operating (GPS) equipment in any a/c other than the ones they have trained
in?

My experience is VERY limited. With little exception, I've trained and
flown IFR only in my owner operated a/c. It was very clear to me that the
button pushing idiosynchroncies of my particular unit (G 300XL) were
specific to not only that unit, but specific to the installation in my a/c.
I would feel confident of being able to operate another 300XL installation
but would be aware that installation options could change certain procedure
significantly.

The 400/500 series Garmins are pretty common and I assume that most pilots
fully trained on one would feel confident operating other 400/500
installations. But I know from the couple of training flights I did with a
430, I never caught up with it.

Ironically, while GPS has made accurate navigation bone simple, it seems to
make jumping from plane to plane more challenging. The moving map
practically eliminates loss of spatial awareness, but the button pushing
required can lead to brain freeze trying to figure out how to make it show
you what you want.