Ars Technica has performed an acceptably complete comparison between an expensive compact camera, a Canon EOS 20D (my current APS-C camera), The Samsung Galaxy S II, the iPhone 4, and the iPhone 4S.
I have frequently discussed my love of the iPhone 4S's camera. It's a real wonder. It is leaps and bounds ahead of every other cell phone camera on the market and significantly better than all of the low-end P&S cameras that I have used. This comparison only confirms that.
As regards resolution, the Olympus XZ-1, with its superb lens, blows everyone else out of the water. The Canon would have made a better showing if they has used better glass, such as the 60mm macro. They bafflingly justified their choice of lens by saying "choosing a different lens, on the other hand, has its own series of trade offs." Yes, like better image quality. Regardless, overall, the iPhone 4S is only somewhat behind the Olympus in good light. Its rendering and lens are excellent.
But the question has never been whether the iPhone is better than a high-end P&S camera. Of course it isn't. The Olympus is still better in every way. The question was whether the iPhone 4S is better than cheap P&S cameras that are under $250. I think that the answer is most certainly yes. I wish that I had done comparisons when I had the chance, but you will have to take my word for it. If your current camera cost you less than $250 when new (not counting Chistmas discounts and the such), the iPhone 4S is better.