Edit: The 4S addressed the antenna problem (aka antenna-gate), so in this case a 4S has an advantage over the 4.
A problem that never existed. I have a 4, as do several dozen friends. Nobody I know has had dropped calls.
The camera on the 4 is fine as well. They had to bump the specs when the introduced the 4s, which was really about recouping Siri costs. They bought that technology, they didn't develop it.
Remember Apple is still marketing the 3, often it's a give away with a contract. They're brilliant at keeping a product out there long after they've recouped their R&D costs.
In a couple of months the iPad 3 will be introduced, much to the frustration of all those who received iPad 2s for the holidays. The iPhone 5 will arrive next summer right on schedule with the 3 dropping off and the 4 rolling down to the being the low end.