Camera+ has thrown together some great comparison photos depicting just how much the iPhone camera has improved over the years.
The comparison photos really speak for themselves, and the difference is especially noticeable with the iPhone 4S photos when compared to older models. They even go on to compare with more expensive DSLR cameras for reference. As expected, from the original iPhone to the latest iPhone 4S model, the camera quality has obviously improved immensely.
Feel free to drop into our iPhone 4S pictures forum for even more evidence of how well the iPhone 4S camera performs.