quicktime pro

definately! its not that much.

you can save QuickTime audio or video from a webpage, copy and paste audio and video so its like a mini movie editor, record video with iSight (although Photo Booth in Leopard now does this), create slideshows and export video, audio to different formats.

so if you converted a DVD to mp4 using Handbrake for you iPod but then wanted to make it even smaller to share with someone you could export it as a QuickTime movie with a lower resolution and frame rate to get the size down.

 

VLC does most of that for free, and it's faster!
QT Pro is nice, many other programs depend on QT (e.g. iMovie, Snapz) and if you go pro it will extend the other programs capabilities to.