Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
It "just worked" for mov. When you tried to open a file without a complete index (everything that was not a mov or mp4) it had to read the whole file, consuming a lot of cpu. And let's not talk about the infamous optional mpeg-2 component, which used a special time of tracks.

Anyway, the new AVFoundation framework can done everything better, it's just that it's not exposed in the QuickTime app, or better, many features are available in QuickTime, but only in the menu, and no one looks at the menu.

It would be quite easy to make a QuickTime 7 clone using AVFoundation, but probably there is no money to be made.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.