Advantages would include, trust, free to use, no download (or at least hidden or managed downloads of widgets), use from within a browser window, and social networking.
Assuming that the features rival VTTs then it would simply make the technology more accessible (could play it at work for example... not that I'd do that of course... probably. Or you could use it on a Mac or Linux machine) and would add social networking directly integrated into the system allowing games to find players and players to find games easier.
Of course, who knows. There is something to be said for ubiquity though.