Google TV is TV over the web, still need a browser. No and yes to building a htpc, You can get dvd players, and these stand alone boxes that will stream netflix movies as well as other content from the web. It all depends what you intend to use / or how you intend to use all the steraming apps.
For my money I've got the PC plugged into the HDTV with a remote KB and mouse, and a netflix subscription.