I have created a page hierarchy like this:
Parent page
- Child page
-- grandchild page
-- grandchild page
- Child page
-- grandchild page
The plug in works perfectly when expanding the first level (child page), but when expanding to the second level (grandchild page), the +/- icons for the child pages don't move down with the page name.
It still works fine, just makes the UI a little confusing :)
http://wordpress.org/extend/plugins/collapse-sub-pages/
(Update: sorry, I just discovered this works perfectly in FireFox - seems to be a Chrome issue)