I've found that when I have a project, and I want to put it "on hold", I'll put it into someday. It would be nice that when it is in someday, that there is some indication whether it is a project, or an individual task. (Sometimes I need to refresh my memory as to what tasks were in the project, to remember why I had put things on hold). So it would be really nice to be able to open and see sub tasks below the project (or at least highlight the fact that it is a project with pending sub-tasks). I wouldn't want all those tasks in the someday view unless I opened the project.
A couple times now, I have checked off a project in someday, thinking that it's done, and then realizing, oh wait, there is one or two more items which aren't completed yet and that's why I was waiting. But since I don't see those tasks it doesn't trigger in my brain.
And I could look under projects and actions, but many times I just want to glance through my someday list to see what I need to activate again, or decide to cancel.