Right, but what I'm pointing out (perhaps not well) is that the fewer inconsistencies you can make in a system, the better. If a user can't handle a file in an image, then they haven't a prayer of figuring out an installer in an image, IMO. Teach them how to deal with files in images, and you've just given them a powerful bit of information for working with the system in general.
Now leverage that for applications, and you've removed one more thing they have to remember.
Wizards are a hack around bad UI behaviours. "Oh well, we can't figure out how to make this simple, so we'll just hand hold the user." :P It's a lazy developer's way out.
What I'd rather see is a dynamic tutorial. The first time a user mounts an image, for instance, a Help dialog can pop up (noooooo! No Clippy!
) offering to give them a quick tutorial on what it is, how it works, and what they can do with it. *NOT* do it for them, but instead give them solid information that they can use. Benefit is also that they user knows that the system has that info in it, so they can know to go looking for it later.
I really wish Apple shipped a simple tutorial with the system like they used to.