On the 300D the Mirror Lockup works on a timer basis. If you enable ML in the extra menu and have the timer set for 6 seconds what happens is... You press the shutter and the mirror flips up, 6 seconds later the camera takes the photo and the mirror drops again. The idea is that you cut down on vibration and get a sharper image.
Further to this, I installed the undutchable hack yesterday and it really does give you RAW in all modes! brilliant.
