"If I had a nickel for every user that asked me how to install software or its update, I'd be a millionaire"
I believe you. I have provided computer support to education institutions for many years, and no end user can understand installers. If you want to stop people asking you how to install something, don't use an installer.
"Installers are simple easier to support than other mechanisms."
This is totally false. The easiest thing to support is a runnable application file. Users deal with these things every day, if they want to "install" one somewhere else, like on their local hard drive, they can drag and drop it there, the same way they "install" every other file they use on a computer.
"Problems arise on MacOS X when some modules are just plain hard to get into the right place."
They do not. If I want the shareware in my Applications folder I drag it there, if I want it in my Documents folder I drag it there, if I want ... Ohhh, you mean it's hard for *the programmer* to figure out where to put the files.
You're right, but someone has to figure out where the files go and what installers do is move the work from the programmer to the user. That's why users have so many problems with installers; they don't know where all these files go. Programmers are in a much better position to know where all the files go than users are, and the programmer only has to figure it out once. With an installer, every user has to figure it out every time they install.
"Although programmers should try to avoid writing software that requires the above, sometimes they can't."
They most certainly can. Microsoft Office is one of the most complicated Mac OS applications going, and installing it consists of inserting the Office CD and dragging whatever applications in the CD window you want to wherever you want to run them. Yes, those applications want to install all kinds of executables, extensions, fonts, sample files, etc., etc., but the application knows what files it needs. It knows where they go, where to get them, and copies what it needs where it needs them. It doesn't ask the user to do it.
Now, no doubt this is harder for Microsoft to do than to have the user run an installer that asks her or him to figure all this stuff out, but it's much easier for the user.
I apologise if this reply sounds confrontational, but when I read "Delivering an installer is a really great idea ... they make users really happy" I was astonished. Not only is this not true in any universe I've ever inhabited, I cannot comprehend how anyone could have this opinion.
Installers are a hold-over from the days when only computer programmers used computers. The fact that programmers still have to go through such contortions to get people to use their programs should be a clue to everyone that something is wrong with the entire concept.