I came across apm/ampd through openbsd. In openbsd, my experience with it is golden, because as far as I can tell, it does exactly what I want: suspend/hibernate as user (by default) with a console command, lid and power button functions, simple textfile configuration (I find acpi's events-for-shell-scripts approach to be more convoluted than apm's), and desktop-environment-amoral. With Linux, on the other hand, apm is "gradually being replaced by the ACPI standard," and I guess it makes sense given that, with the right adjustments, acpi can perform the same functions.
Nonetheless, apmd is still in the Debian repositories, and its kernel option still exists (albeit disabled by default). As recently as 2015, I can find posts about users who still used it, including one who tweaked his or her kernel in order to support it. However, I'm also aware that lots of changes Linux in general, and Debian and particular, have occurred in these last three years.
I haven't been able to find anything along the lines of "apm in openbsd vs linux", so it's nebulous how un-alike each operating system's own apm is compared to the other. I suppose the best answer would be, "recompile the stock kernel with apm enabled and see for yourself." However, dasein used to say that it's easier to learn from others' mistakes first; so I wanted to open it up here before I did any kernel-building for something that may end up being wholly undesirable.
Do you still use apm? Why?
Have you used it before and currently prefer acpi? Why?
What advantages does acpi have over apm that would be useful to know? (Maybe something more obscure, undocumented, that you found out "the hard way.")
If apm were enabled by default in your kernel, would you use it over acpi?
If you have any experience with openbsd, is there anything I should know about the linux/debian version vs. openbsd's?