The iPhone 4S is the best phone you can buy right now. That's been true of every iPhone, really.
The other thing that's been true about every new iPhone, except perhaps the iPhone 4: Most of the fresh magic is in the software. When Steve Jobs announced the original iPhone, he said the software is "five years ahead of what's on any other phone." It's kind of crazy that he wasn't far off, since it's taken nearly five years for other phone software to even come close, with the latest Windows Phone and possibly the next Android.