I had not planned to take my iPhone on the trip to Europe as my phone is locked to Rogers. The roaming rates are too expensive to use the phone in Europe. But we needed the phone in Montreal to call our travel agent to help book the connection in Madrid to catch up with our tour. So I had to bring the phone.
While I could not make any phone calls, it has served as a way to send and receive emails and surf the web using Wi-Fi in airports or hotels.
It also came in handy to type in our travel journal each day. This way I can import the journal as soon as I get home. It is better to write notes each day than trying to remember it later. Typing it on the iPhone each day is much better than trying to transcribe my hand-written notes a few weeks after we return.