A quick real world audio test using the latest Canon 2.0.3 firmware for the 5DmkII. This was an interview during a visit by UK Foreign secretary David Miliband to China.
Audio was fed from a reporters mic with a Sennheiser radio transmitter to my Sound Devices MixPre audio mixer, then using a Pinknoise systems special XLR to minijack PAD cable to the 5DmkII.
I'm not convinced of the strength of the minijack connection in busy news environments like this and I'm worried it may fall out or become dislodged. For that reason I actually set the record level in camera at just under half way on the meter. This is a compromise I've adopted for news so that if the jack does fall out I still get some sound from my internal camera mic. There is some hiss due to the camera's noisy internal preamps, but I can live with it.