I do my serious shooting with a 5D III, but I had been looking for a while for a small, lightweight camera for family pics and travel. I had considered a high end compact but it somehow seemed too much of a compromise, particularly in operation (shutter lag, viewfinder, etc). When the SL1 came out it seemed an ideal solution, and after having spent some time with it I can say that for me this camera (with the 40mm pancake) is almost perfect as a lightweight complement to the 5D/III. The great thing, for me, is that both cameras share so many things - the optical view finder (obviously), the Canon layout of the buttons, and the general shooting method. The only real difference in operation is the lack of back button focus (and the lack of the second wheel).
I feel Canon produced a wonderful little camera in the SL1, and for me it is the perfect "informal" complement to the amazing 5D III. I figured others might be wondering about this so I thought I'd share my positive experience!