QuickTime X is a significant update. For consumers, there won't be a Pro version. Any version will allow simple editing, video/audio capture, and allow you to "publish your media to MobileMe or YouTube -- without worrying about codec formats or resolutions." We're not sure if you'll be able to save as a QuickTime movie or source file as before, but the removal of some previous limits will make QuickTime the snappy iMovie substitute it could be. Plus, QuickTime X will allow you to use any web server to stream live video over HTTP. Can't wait to see what people do with that.
In addition to the visible changes, QuickTime X looks like a fundamental rewrite of the application and its underpinnings. Support for Core Audio, Core Video and Core Animation could mean some really interesting things for the future of media playback (not that we weren't promised as much a few years ago, of course). All of this comes wrapped up in Snow Leopard, and takes full advantage of the speed-tuning tech therein.
Jump three spaces forward!