E-M5 - 16x9 aspect ratio question

I've read that the sensor is a 4:3 - but I'm one of three people on the planet that take nothing but 16x9 stills. dpreview in one spot shows 16x9 as being supported, and in another omits it... Does anyone know what the max 16x9 resolution of this camera actually is, and what are the downsides of shooting in that resolution? (eg. are images cropped significantly, viewfinder becomes difficult to use etc.?) Man, this camera seems like a great replacement for my GH1, but I need 16x9 to be happy! Thanks...