Google has launched some cool metrics tools for YouTube which are available to anyone with a YouTube account. YouTube Insight will give you information about how often a video is viewed in different geographic locations, and compare its popularity to all videos in that region over a given period of time.
You can also track video performance over time - for example how long it takes for a video to become popular.
You can find currently available metrics by clicking under the "About this Video" button under My account > Videos, Favorites, Playlists > Manage my Videos.
Insight into YouTube videos [Official Google Blog]