One developer's perspective:
Hadley:
All of the things you mention in your first paragraph are the responsibility of the application. Generally speaking, you'll find issues with them most often in Carbon apps.
That said, there does appear to be a bug in the OS function that handles dragging windows in Carbon. Specifically, under certain circumstances it does not respect the "bounds rectangle" that is passed to it. As a result, you can drag windows under the menu bar.
Respecting the dock is a clearly documented application responsibility. Any app. the violates the dock probably wasn't tested enough as the solution is quite simple.
Command H is handled by the OS unless an application has it mapped to something else. This is real dilemma for developers who may have a user base with years of history using CMD-H for something else.
Cheers,
-bc
What Panther Should Fix: Part One, Broken Windows