Wonderful little cams
The narrow head width of these allows them to fit into the type of shallow cracks typically found at Joshua Tree (where I climb most often). They are, however double stem, which means they are laterally stiff - you have to be careful with the placement angle to assure they don't torque out when loaded. On the bright side, this lateral stiffness makes them easy to place, I generally retract the lobes, slot the cam behind a small constriction, then release the trigger for a sound placement - kind of like how I place a nut.
One key advantage to these over nuts is that they can withstand pull from a greater variety of directions - this makes them a good first piece on a pitch to prevent the "zipper effect", and makes them more versatile in a complex belay anchor. They are also much faster to place, and more forgiving than a nut of a similar size, but unfortunately require a better eye to evaluate properly than a similar nut or larger cam.
I have taken a fairly high factor lead fall on the Red #1 (2nd piece, 8-10ft fall with 15ft of rope out, high impact force Mammut 10.2 rope) and not only did it hold solidly, but the cam remains totally functional. Although I totally trust the larger sizes, I personally don't carry the gray 000, as I wouldn't feel comfortable leading above it anyway.
It is also worth noting that I always carry the Yellow #2 C3 and rarely the blue #.3 C4, as I find it fits better in more of the same placements.