Beware - using WiFi while roaming
If you subscribe to a global data plan and use WiFi when you are roaming, then you have to turn off the data roaming when you are using WiFi or you will get charged for the WiFi data. There seems to be no way to set priority for networks (i.e. use WiFi when available over data)
Unfortunately, turning off global data roaming requires going into settings, data manager and turning it off, which isn't convenient. This seems to me to be a pretty basic function that I had in my previous HTC global smartphone...
I will say that so far, I've found Verizon's global data roaming plans to be reasonably priced and work well. just a few dollars a day, which when you are travelling overseas, isn't much.