I've done an unsual amount of traveling (for me) this past month. I spent two weeks in Taiwan and after returning to the states for a week I traveled to Seattle. These trips allowed me to test my travel gears including the Android G1 phone and the iPhone.
I have had the G1 for awhile but no phone service for it. Since it is unlocked I decided to get a SIM card for it in Taiwan and use it while I was there. Getting and installing the card was super simple and I did it at a 7-11 store. It was a matter of putting the card in and turning it on.
As a phone device I found it to be excellent. Sound was clear and it was easy to use. The screen was sharp and overall responsive. One annoyance was that it accidentally dial too easily unless you lock the touch screen. The other annoyance was that the contact list was not easy to navigate and search. I am not sure why Google struggles with contacts on both its site and the phone.
The camera on the G1 is super especially compared to the iPhone. With 3MP and autofocus, it is a real camera. Its excellent intergration with Google means that it can hold its own as a PIM. Add to it the wifi and browser capabilities and you have a nice portable computer that fits into your pocket. For traveling, the G1 is very well suited.
The screen can be a bit larger as it's current size limits its use as a portable dock reader. The UI of its apps are not as uniform, and Android is not as polished as the iPhone. Its marketplace needs to be improved so more apps get built. Battery life is short and needs improvement for it to be a true road warrior.
The experience of using the G1 vs IPhone is like using a PC vs Mac. The advantage of a open platfom is variety but initially a less polished user experience.