I just added global data roaming to my iPhone after a series of trips to Europe since the 3G models came out. I resisted. I have Nokia N and E series phones to use, as wells as my Blackberry Curve. But my dependency on so many apps that the iPhone has that work easily has won out.
Many of these are travel related apps, and while they likely also exist for the other platforms too, finding them, keeping them up to date and not having OS conflicts made the decision simple.
Unfortunately this means I'm now carrying three devices, not two (or really one.) Why? Well for starters the BlackBerry offers me the best email experience on the planet and at the lowest annual rate. The Nokia's offer a better voice calling experience as I can SIM swap from country to country, but it's the App Store and the apps on the iPhone that bring the idea of Web 2.0 to widgets that wins out. All my flight apps, my Tube and Metro maps and routing, booking restaurants via Open Table, doing foodie research with Zagat, etc. are on the iPhone. Plus I can use Truphone and Boingo so easily with it, that I'll be calling more and paying lots less.
So, for the next two months I'll pay AT&T a whopping $119.00 to give me what I need as I have two trips to Europe on an extended period. When I'm done, I'll turn it off, and reactivate that as needed. It's only when I can get a true unlocked, not a jailbroken or SIM-Shim iPhone that I could cut back to two.....but thankfully, the iPhone is slim and light. I'll survive...I just have to remember to turn off "push" and also not have it called by Grand Central.