By providing a framework for fills and strokes, SVG can match the output of other traditional design tools. Offering more complex features like transparency, gradients, and patterns allows it to compete head-on with other sophisticated formats. As SVG provides designers with a complete palette of possibilities, there is little that can be rendered in other applications that cannot be rendered in SVG.
With your newfound ability to paint objects, the next hour will teach you how to create and use symbols. Symbols have become popular in other design programs and technologies thanks to Flash, and the W3C was sure to include such a useful component in SVG.