The plugin is still in beta phase. The actual export will take a few seconds longer for a 20 subtitle track feature movie.
The plugin creates a reference movie to save time and disk space.
QuickTime Subtitles - a glance from the future
A new subtitle format is coming to QuickTime
Update: See how it works with our new export plugin
The movie here here will show you how you can prepare a movie containing 20 selectable languages with Annotation Edit.
For iTunes/iPhone/iPod Touch or Apple TV export to a compliant video format before applying the subtitles.
Please note: To try it yourself please install the beta of our QuickTime Subtitle plugin first.
The information how to do this is partially taken from the Apple discussions forum.
Please leave feature requests there.