myTV - Personal YouTube Theater is a YouTube video player. It is more of an entertainment hub. It is not an application that you would use to simply browse YouTube. Instead, with it you can access certain YouTube channels and see their videos quite easily.
When you first launch the application, you will be asked to select a TV provider. I simply accepted the one that was included by default, and then I figured out that it was a YouTube channel. From the settings you can get your own channel if you wish. The default one has a lot of nice content, which you can access from the buttons on the left. There are three main categories: MyTV, News and Entertainment. For example, the News category features videos by CNET, Adobe TV and MAC World. The Entertainment category has movie trailers, reviews and more.
The application works mostly well and it allows you to play HD and SD videos in fullscreen mode. I noticed that you couldn't close ads and that while ads were active (they go away after a while), you can't seek the video (advance or rewind, if you will).