I learned another limitation on a vacation last year to DC. Where it turned out I didn't remember to bring the charger along for my P&S.
Battery life is poor on the iPhone when you take pictures over the course of a day. Especially if you extend the screen lock time so you don't have to unlock for every picture. On 3 days at least the phone went dead by the time I returned to the hotel room.
I ended up buying another charger for my P&S.
On the other hand, the day I went to the white house, where you couldn't take in a camera at all, all I had was the cell phone. Couldn't take pictures in the WH, but at least I could take it along.
Wish I had just taken the DSLR along on this trip instead of the P&S. But when I'm flying it is a pain to carry stuff like that. The P&S fits in carryon with the computer much better.