[billobermeyer]

I'm working through the tutorial and I have run into two issues at Step 11. One seems bug-like to me, the other -- not so much.

The first (and non-buggish) of these is probably due to my confusion about what I am telling the program.
When I highlight "effort" in the Task Information Inspector, I think that I am setting the amount of effort that the task requires. Conversely it seems to me that when I highlight "duration" in the task inspector I am telling the program "the task takes this long". Clearly I am wrong (according to the tutorial and my experimentation) since the duration is changed when more resources (?effort presumably) are assigned to a task whose duration I have "set", but not when I have "set" the effort required. How should I be thinking about this?

The second issue may or may not be related to my confusion (above).
For the task "Paint bits" (1 h duration) I assigned "Me" (Staff).
Duration remained at 1 h. So far, so good.
I assigned "Paint" (Material) to the task. Still 1 h. OK.
I then assigned the "Airbrush" (Equipment) to "Paint bits" and the duration dropped to half an hour. That seemed strange to me. I expected duration (even with my imperfect understanding, see above) to be affected only by the assignment of more staff -- or at most by more than one of a given resource.
I then created another piece of "Equipment" - a "Room" and assigned that to "Paint bits". Duration dropped to (<0.25 h) which is really confusing. Since adding the airbrush changed the duration, I was not surprised to see duration reduced (though, why?) by adding a room. Even so, I thought that the duration should still be 20 minutes (1 h / 3 resources) rather than under 15 minutes -- unless the resources are being treated very differently.
What's happening?

Sometimes more resources can make the job go faster (as in your example of adding to the number of people unloading boxes).
On the other hand, think about driving a nail. You need a person, a nail, a board and a hammer. Without one of each the nail does not get driven at all. More than one might drive more nails, but won't "drive a nail" any faster. Is there a way to explain the difference to OmniPlan?

Thanks for any illumination.