I've only tested the Live View function to see how it works, but I can already see how useful it's going to be in studio and macro shootings. Just a note, you can't half-press the shutter to autofocus while in Live View mode. You can either manual focus, or use one of the two autofocus methods, quick (the mirror flips up, the LCD goes dark for a short while, and flips down with focus locked) or live (the camera uses the LCD's contrast detection to achieve the focus--this method is slower than the quick method), both by pressing the exposure lock button (*) while in the Live View mode. Using either the RS-60E3 wired remote or RC-1 wireless remote in Live View mode will ONLY trigger the shutter, and has no bearing on focusing.
Some people seem to be under the impression that the inclusion of the Live View feature will enable them to use the XSi/450D as they do point-and-shoot digital cameras, to compose their shots. That is not the case. You can't really make a functioning use of the Live View feature unless the camera's securely mounted on a tripod or on a flat surface. Both Live View focusing modes, while precise, are too slow to be used for hand-held shooting.