When shooting in Live View mode, you use the AEL/AFL button (autoexposure lock/autofocus lock) instead of the shutter button to focus. Since it flips the mirror down and up to do so, the accompanying "thunk" takes a bit getting used to.
In an inexplicable design decision, Olympus removed the one-touch functions it traditionally doubles up on the navigation buttons in its higher-end point-and-shot cameras. Now, pressing on the OK button pulls up a single screen in which you change all your shooting settings. It's just as easy to use, but I would think that Olympus would want to stick with the familiar for the entry-level users it targets with the E-410.
Photo Credit: CNET Networks