Few thoughts:

Quote:First of all, it complexify you program, as it forces you to handle edge-cases, for example if you don't make use of long options, or subcommands.

This is basically developer experience vs. user experience. It's true that you probably should not use all of these for simple scripts, but on the other hand, simple scripts don't need to be "great CLI apps". Great software requires great user experience, and handling these common cases is not that complex.

Quote:Moreover, it's said that the help text should display common usage example, and detail the options.
This is noisy and unhelpful

This is completely subjective, but I'm fairly certain that most users greatly appreciate writing out at least the most common use case and few options.

Quote:Manpages are the only reliable documentation you can get offline.

Yes. Luckily --help and man pages are not mutually exclusive. Both is best.

On error messages I mostly agree, though you should probably consider greater detail on more complex cases.