I'd like to be able to apply an action on the fly...meaning that I don't want to have to add it to the actions dialog and have it saved.
An icon in the context menu and tool bar that opens up a quick "find and replace" dialog would be perfect for those quick one shot renaming needs that arise every so often.
Also an "Mp3tag on top" function would be cool. I'm using Actual Window Menu to achieve this right now but it's a feature that should be in almost every program by default.
And "Minimize to tray" would be convieniant.