I have been very succesful using the mirror lockup w/self timer mode approach.
When you press the shutter release the mirror locks up and the timer counts down 2 seconds before exposure.
When I'm on a landscape shoot I often program the C mode on the 5D with these settings, so it's quick and easy to throw the camera on a tripod, switch to C and be set to shoot with mirror lockup and 2sec delay. Pull the camera off the tripod and then switch to the exposure mode of your choice (P, Av, Tv, Man etc) for handheld use - without mirror lockup or self timer. Very handy.
S