I have one thing to add to the discussion of separation of AF operation, and release of the shutter, working with a remote release. I'm a BBAF shooter, who removes the AF from the shutter button. I would like to be able to do the same while using a remote release. This is not possible since the remote contacts are pretty much wired in parallel with the shutter button, so to use a remote switch to initiate AF you have to have AF on the shutter button.
I thought I could get around this by wiring a remote lead with two separate buttons, rather than the usual double press you normally see. You can use the button to initiate the AF, and then press the shutter button to take the shot without any problems while you continue to AF. The problem comes if you want to shoot without the AF active, pressing the shutter release button, without the AF active, causes the camera to initiate AF and then fire the shutter. This was never an issue with my old 300D, with the 3.5mm TRS jack. I could use a footswitch with a TS jack positioned so that it contacted the ring contact in the camera to fire the shutter, without initiating the AF. The 300D didn't offer BBAF though.
Mostly when I use the two button release I built for the 50D the AF initiating isn't a real issue, since I would have the AF active anyway. One of the main reasons for building it is that I have Peripheral Neuropathy, which affects the feeling in my fingers. I often find that it is difficult to determine where the first and second presses are, and will press all the way. The click on the camera is not too bad, but many remotes I have tried have had much softer buttons.