Yes, indeed... I failed to familiarize myself with software architecture with appeared to be at least very similar to the Garmin Aera 500 I have been happily using for years, and the G 1000 I have flown many times. As I fly only VFR, and usually in a locale I know well, I have never needed to use these very advanced systems for any purpose other than back up situational awareness.
When I compare the terrain and obstacle presentation of the GTN 750 and the Aera 500, they appear to be the same, but unless you change default settings in the 750, it does not function as the 500 does. I am far from a software wiz, so I spent a lot of time reading the manual, both before the flying, and during, while I was right seat. However, in hind sight some of the differences which I later found to be rather important to me, did not leap off the page at me. I did receive two hour hour training sessions of the Garmin systems in this aircraft, one with the installed, and a second with a visiting Garmin rep. That left me feeling fairly confident about my ability to use the system in a VFR environment. But, although I have been evaluated and found competent to fly very complex GA aircraft, there seems no mechanism to assure my competence with an even more complex optional system in these aircraft.
This is where the lure of automation begins (for me anyway). I am presented with what appears to be an incredibly capable system, without the caution that to receive the full benefit of that capability, I'd have to reset a number of default settings. There does not seem to be a "checklist" to be fulfilled to assure that the important elements of the system are understood by the pilot, for the environment in which they will fly. This is a miss....
The operator's manual for the GTN 750 has more content than several Cessna flight manuals combined! We have pilots who fly planes without reading and understanding the whole flight manual, so understanding and being able to recall the contents of a many hundred page system manual is not assured.
For me, two misunderstandings took place, which were relevant to my failing: Unlike the Aera 500, which displays obstructions out to a 50 mile page zoom, the GTN 750 was preset to stop displaying them beyond a 5 mile page zoom. So I'm trying to optimize my situational awareness in a 20 mile approach area, and for lack of understanding this function well, I cannot see the airport and obstructions at the same time. But nothing prompted me to know this, other than my realizing "some wasn't right". Approach in poor conditions was not the time to figure out why, so I stopped placing any dependance upon it.
Similarly, the Aera 500 will allow me to "draw" a waypoint between my present position, and same destination. The GTN 750 will not. It has an "Insert Waypoint" function, but after trying and failing, and later reading the book for that, it turns out that the functionality is not the same as the Aera 500, so I was doomed to fail at what I was attempting.
So, as my primary role was mentoring my friend in his plane, I spent literally hours optimizing the settings of the units to his needs, and briefing him in great detail as to what I had set, and why, and how he should use it. I explained what not to attempt (appropriate to his experience level), and that he is to ignore the system if he becomes task saturated. He is not a good English reader, so I could not depend that he would read and understand the operator's manual for these systems.
In the final analysis, when I could most have benefited from the additional capability of the automation in this aircraft, I relegated it to low level advisory, while I returned to much simpler systems, I knew very well, and it worked.
There will be a future shift, where new pilots will devote the immense effort required to be conversant with these automated systems as a part of their basic pilot training. During this process, will they become conversant with the differing software architectures of different manufacturers? Will they retain the much more basic skills to continue an adequately safe flight using only the most basic backup systems (needle ball and airspeed, VOR, ADF and localizer)?