One of the many reasons I love my iPhone is that it takes excellent pictures, eliminating the need when I travel to pack a camera. Less weight, less baggage, less to remember, less to think about...especially compared to the Nikon camera and lenses I carried each day on our 1987 trip to Israel (the photo above, taken by the lovely Robin--using yet ANOTHER camera--gives only a glimpse of the camera and bag, both hanging by straps from my neck).
So on our most recent travels, it has been a delight to use our iPhones as cameras (though we remove the SIM cards to be sure we don't incur any unexpected charges from incoming texts, calls, etc., while in a foreign country).
Still, we did discover one disadvantage on our 2010 trip to Jordan, Israel, and Egypt, which we have kept in mind ever since. While I was actually exploring INSIDE one of the ancient pyramids at Giza, Robin wandered around the amazing site with friends. At one point, however, she wanted a photo of just her with the pyramids in the background, and our friends were off doing something else. But that's not a problem, as there are numerous young boys at the site, eager to perform nearly any task for tourists, in the hopes of getting a tip for their efforts. She started to ask one of the boys to take her picture with her iPhone, when it dawned on her...the device (unlike many conventional cameras) may just have been too tempting for the kid. He could have run off with it and disappeared into the crowd, losing not only the phone itself, but all the pictures she had taken in the previous days of our tour.
To date, I think that may be the only disadvantage we've discovered in using the iPhone as our small-but-high-quality travel camera: you can't hand it to just anyone to take your picture.