like hownowbrowncow said: depends from chin to chin. When i bought my chins more then a year ago, the breeder said not to put houses or other real enclosed hiding spots in their cage to avoid making them skittish.
He said that a chin who can flee (weird noise, sudden movement around cage for example) will always do so, and if they lack the possibility to hide somewhere they develop a more curious and relaxed nature cause then they will check out what the possible danger may be before trying to take a run.
The day i hung some hammocks in there (in a double level ferret nation there are 2 hammocks per cage) they immediately explored, and after some munchie encouragement they sleep in it, play in it and use it as a lookout post.
The reason i put up hammocks: they give your chin some extra space! The room used by the hammocks is void anyway since its at the top of the cages.