At the moment, it's just:
<Track name> (without anything else)
"Artist" followed by <Artist name>
"Playlist" followed by <Playlist name>
You can also double click the icon to shuffle playback.
Playback controls (next, previous etc..) might be there in an update. It wasn't an efficient way of controlling music because it wasn't always working nicely with Zune. It's more efficient ot embed Zune in the taskbar. You can do this by right clicking on the Taskbar...Toolbars...Zune. Then minimise zune and all the playback controls are immediately accessible from the taskbar :)