I've been testing with Raw Developer. Very nice. Almost to much control! The main issue I have, is that when shooting tethered using Canon EOS Utility to fire the camera, I can't merely refresh the Raw Developer window after exposure to get the thumnail to show up. I need to go to the Raw Developer menu bar and manually reselect the File>>Open. Also, after doing that, the thumbnail window jumps to the other end of the row of thumbs making me need to scroll back across them all to view the current capture.
I have tried using PhaseOne COPro v3.7.9 with a 1DsMKIII. PhaseOne COPro v3.7.9 supports 1DsMKIII files, but not tethering. I use the same EOS Utility to shoot, and all I need to do is refresh the PhaseOne window with a mouse click, and the current image pops right up.