That easy? So it automatically knows to route through the video card's HMDI port?
Yes, Any 2000HD series and up (3000, 4000, 5000, 6000) has it's own separate audio chip on it. If you are running your audio through that chip, then you will have audio going through the HDMI cable. If I remember correctly, all of the 5000 series and up also decode Dolby TrueHD and DTS-HD through that same way as well.
Just keep in mind that it is using the Audio chip ON the video card itself and NOT routing the soundcard's audio through the ATI card and then through the HDMI.