Greg,
I don't think the 50D does HD. It's 720p. The 5D Mark II does 1080p and looks incredible.
With the latest firmware update you can now control aperture, ISO, et. al. Full manual control.
I've made some short videos with my 5D Mark II but don't have the right hardware to view the videos natively right off the card. My poor notebook is too old.
Regards,
Humayun