Our WPMU dashboard has only an "add media" button.
My personal WP dashboard has "add image/video/audio/media/poll" buttons.
Is this the way it is, or do we have a bad WPMU install?
If this is the WPMU dashboard, must we turn to plug-ins for video, audio and poll uploads?
You're in control of which are displayed. Go to Site Admin > Options, and see if the "Upload media button" settings for Images, Video and Music are checked.
http://edubuzz.org/screencasts/wpmu-upload-media-button.png
Also, the sole "add media" button still gives you the same uploader.