QClip allows you to play QuickTime movies through QuickTime-compatible video hardware such as FireWire devices, Decklink video cards and AJA video cards.
QClip offers fast access to any QuickTime movie on an external device, and is mainly designed for serious video editors or those that have to broadcast in QuickTime format. However, to connect this version to external hardware, you need to register the software first. After that it's completely fully functional.
You may also be disappointed if your graphic card is not QuickTime compatible. For most users, this won't be a problem, but there will be some that won't be able to playback anything at all. QClip is mainly useful for those that are working in a live studio or broadcasting environment, so it won't be much use to most general users. This is because it supports batch importing of clips (to make it easier to get clips on air) and therefore allows you to use your Mac as a broadcast server for someone needing to access the clips using QuickTime from another location.
If you're in the broadcast business, and need to playback QuickTime clips on external devices, then QClip adds more power to your elbow.