How easy is it? Let the developers at Google show you:
Unlike Skype, by incorporating the chat directly into Gmail, all that is needed is a simple plug-in and you're ready to go. This plug-in keeps the size of the application down to approximately 2 mb and uses a proprietary format rather than flash, the common format for other chat programs. The benefit to this design is the how the two computers communicating connect. Instead of the traditional point-to-point design, all the traffic from Gmail Video and Voice will run through the Google servers. In theory this should provide better stability and ease the strain on your computer.
While having (almost) everything bundled into one log-in space, chat, e-mail, voice, and video, don't expect this to completely replace your other video chat programs depending on your usage. One limiting factor is the inability to connect to regular phone lines, a handy feature in the paid version of Skype that is frequently used by many in the business realm.
Will the bare-bones, but easy to use Gmail voice and video chat prove to be a big success, or will Skype continue to dominate the market?