Colomban Wendling's Commander plugin [1] also supports switching between open files, even though this is not documented. However, to limit Commander to display *only* the files, you have to type an "f:" prefix (likewise "c:" for menu items). Personally I find this cumbersome, so I use a straightforward patch that adds keybindings for limited modes (not sending this upstream yet because it needs more UI work).
Colomban, do you think these two features -- symbols from the current document, and keybindings for limited modes -- would be good to have in Commander?
[1] http://plugins.geany.org/commander.html