+1 for me. I've really come to like how Evernote keeps me on track with my projects. But having too many details that are important, but aren't required to be visible all the time can complicate my workflow.
I could create separate notes for each and every item that I would like to collapse and create links to them from one main/master note, but I get weary about creating so many micro-notes that they get lost in the shuffle. Expand/Collapse sections would be super handy to keep major themes in one, core note.