My earliest experience was with the flying club where I learned to fly, and rented post PPL. I kept myself current by flying their 172RG at least once a month. It was offline one day when I went to take it, and I told the dispatcher that I would take one of their many 172's instead. I was told across the desk (and in front of my passenger to be) that "I was not checked out in a 172". I immediately had a chat with the manager (who had done my PPL flight test the previous year) and followed my patronage of the club. He quietly gave me a blue card, and said present this, you won't be asked about your currency here again, keep yourself checked out.
I have had all kinds of experiences with checkouts, but most memorable are the checkouts which were very brief, or not requested at all, rather than being burdensome. I think to the many things I have not been asked to demonstrate, if a checkout was even asked, compared to what I want to see when I fly a check ride for someone else. It tends me to think that these other check pilots are either awesome at extrapolating their understanding of what they do know about my flying skills, or, they are simply doing a wave off.
Here in Canada, seasonal changes in flying become a checkout issue, in the spring, many float pilots need a spring float check ride. I used to do those, after I checked myself out first! In the winter, ski operations, for the pilots whose planes came off floats in the summer.
With the right check pilot, I have always viewed a checkout as not only a time to assure my continued skill, but also to perhaps learn something, and I have always tried to be the source of some added knowledge when I have done a checkride, so the pilot comes away feeling that it was a beneficial, rather than punitive flight. Nearly always, I have been able to learn something, though occasionally had to dig a little. If the checkride is going short, I try to think of some questions I can ask about the new type for a post flight debrief.
In Canada, many decades back, while I flew as a PPL the Aztec and Cessna 310, both being over 4000 pounds, they were type endorsed on my license - type signoffs no longer exists in the Canadian licensing system for fixed wing under 12,500 pounds. Land/sea, and multi engined are endorsements, and I'm aware of a "high performance" signoff/endorsement, but am not familiar with that - but certainly agree! But, as I encountervery advance new avionics systems in otherwise simple airplanes, and consider the Diesel powered DHC-2 Beaver I'm involved with testing, I consider the gap between trained (and maybe stale) grass roots pilot knowledge, and the knowledge which should be there for the new systems. Should these new systems be checked out/endorsed to the candidate pilot? Is this an insurance or licensing driven need?
Last November I had to test fly a (new to all of us) 182 amphibian, with a new combination mods (the reason I was test flying it). The insurer just asked for my pilot report, and insured my. No checkout whatever. I find that this airplane has a combination of mods, and background systems which are quite demanding in terms of pilot interaction, and, in my opinion, requires pilot familiarization. Fortunately, in this particular case, I will be writhing a custom flight manual supplement for the airplane, and probably flying some pilot familiarization for the two pilots who will fly it. But I see a new horizon of technology and differences in our legacy types, which I think requires a review in thinking about checkouts and post PPL pilot training for these systems.