In the end, the iPhone 4S offers convenience—light weight, fits in pocket, simple controls—along with competitive, if not excellent, image quality. Unless you need or want full manual control or greater versatility in lens options, the iPhone 4S certainly makes a great photographic tool.
I’ve always been a user of mobile cameras, even when I was a Nokia fan. The iPhone 4 was the first phone cam that really gave me good photos, and I have no doubt the iPhone 4S—and future iPhone 5—improve on it. In the end, the best camera is still the one that’s always with you.