As Google Blog notes, there's now a Google Video Player for Mac. Why would you want to use it instead of QuickTime? Now you can buy videos from Google Video Store, browse scenes within a video using thumbnails and play the video without waiting to download it completely.This is the third Mac software produced by Google, after Google Notifier and Google Earth.
Related:
Google Video Store launch
Download videos from Google as AVI (for Windows users)
Play and convert any multimedia file (free software)