Valve's Steam gaming platform uses Webkit to render their Store and have a 40-million strong userbase at most recent count http://gamespot.com/news/steam-crosses-40-million-users-6348...
https://developer.valvesoftware.com/wiki/Chromium_Embedded_F...
(Unrelated: their embedded Chromium seems to be hard-coded to Windows-like shortcuts; even in the address bar)