I was at a birthday party, and I had my LX3 with me... and also my SB800. When it came to taking a group picture up a staircase, I turned on the LX3 flash, but it was not able to reach to the back of the staircase... so out came my SB800 to the rescue!
I turned on the SU-4 mode (optical slave) on the SB800, set the focal length to 105mm, turned the flash head 180 degress (to have the optical slave face the LX3 flash), and with the left hand holding the SB800 with the flash facing the back of the staircase, and the LX3 on the right hand to take the picture... *click* and here's the pic! The SB800 was on manual mode, and I tested the power of the flash till I got the exposure I wanted.
The picture was taken at night in a badly lit room, but with the simple use of an LX3 with an SB800 on optical slave, you can light up the picture like it was day. Quick and fast... done in a minute!