We were quite surprised to see obvious vignetting at the telephoto end of the S5 IS's zoom. (Though apparent to us on the gray grid, the inset in the middle is designed to make it easier to see at the small size; I used a solid red overlay and difference blend mode in Photoshop.)
Mild barrel distortion isn't too bad if it's symmetrical; when it's asymmetrical, like this, it can get seriously disorienting. Several photos where I knew I had aimed dead-on had a perspective as if I'd shot from the side. Here, the S5 IS's lens squeezes the left side vertically, though the right side is straight. (Shot at 36mm-equivalent; guidelines overlaid in Photoshop.)
I was quite pleased with the color and exposure of the S5 IS's photos. It provides plenty of latitude, and renders saturated colors without overdoing it. Processing artifacts reduce the apparent sharpness of the photos when you zoom in, however.