The result isn't that great - you can't type or read comments if you put the video in full-screen mode scrubbing doesn't work very well and the video pages have a lot of wasted white space. Instead of a clean, fast app for discovering and viewing YouTube videos, Mac users must rely on web browsers and the YouTube site.
Developer Saied Ghaffari of It's About Time was perplexed by something recently while there are good dedicated YouTube apps for iOS, there's nothing similar for OS X.