Today's CVS of Cupid has tag support. Currently works for Ogg and AVI, but I'll add it to other formats as I see fit later on, if the format supports it, that is. Should release 0.0.2 sometime soon, since it's had quite some updates and fixes since I released 0.0.1 just after newyear.
I also decided to have a look at the new APIs of the day and try to update Cupid to it. Noticed that GtkFileChooserButton cannot do save actions (filed as #164900), which means I need to continue using GnomeFileEntry. GtkUIManager (replacing GnomeUIInfo) keeps confusing me for some reason, maybe I need to look for some hello world example code (which http://developer.gnome.org/doc/API/2.0/gtk/GtkUIManager.html basically is, but not just yet). GtkTextView looks nice, but is incredibly complex if you just want a simple HTML-like textbox. How do I get the complete text from the GtkTextBuffer...? Need to move over to GOption (instead of popt) at some point too, but GStreamer doesn't use it yet, which is kind of annoying. I guess I'll quietly continue to use deprecated widgets/objects for a while longer until I get familiar with the new ones...