We traveled in Germany, Austria, France and Switzerland in June 2014 and used Verizon Global Data primarily to help us navigate while driving. Navigation using the Maps app on an iPhone 5 was highly accurate and a life saver on complicated routes (e.g. driving into the center of Vienna). Only once did it send us 11km in the wrong direction on a freeway to make a u-turn.
We put key locations like hotels into Contacts before the trip. That made it easy to go into Contacts on the phone, tap the address to bring it up on Maps and get directions from our current location to the destination. On long freeway stretches we put the iPhone into Air Plane mode to conserve data. Thus we used the navigation to get out of town and to a freeway, switched cellular off for the freeway stretch, and then switched navigation back on when we were approaching our destination city. In that scenario a typical journey would consume 3-5 MB.
To get the Maps app to give you directions in terms of kilometers instead of miles go to Settings > General > Region Format and switch the region from United States to the region you are in, e.g. Germany.
Details of how Verizon Global Data billing works are not clear from the website. The website doesn’t explain how the charges and allocations interact with your billing cycle. This matters, if as in our case, the first part of your trip is in one billing period and the latter part of your trip is in the next billing period. I would describe the billing this way: when the service becomes active (you choose the date) you are charged $25 in that billing period and you receive an allocation of 100MB. If during that billing period you exceed the 100MB allocation, you are charged another $25 and receive another 100MB. The important point though is that any part of an allocation that is leftover at the end of one billing period does NOT carry over into the next billing period. As soon as the next billing period starts you are charged another $25 and your allocation is set to 100MB. In the description above I ignored the possibility of starting the service with a pro-rated charge and a pro-rated allocation. For example, if you start the service in the middle of your billing period you could choose to begin with a $12.50 charge and a 50MB allocation. The catch there is that if you go over the 50MB near the end of the billing period you trigger a $25 charge for a 100MB allocation none of which would carry over to the next billing period.
To track your data consumption on the iPhone go into Settings > Cellular, scroll to the bottom and Reset Statistics. Do that when you begin your trip and again when a new billing period starts. If you want to record the statistics before resetting, take screen shots. When you are outside the U.S. using the Global Data service you are roaming on other carriers networks, Verizon’s #3282 method to report data usage is not applicable or available.
Call Verizon Global Services customer support directly to set up the service, ask questions, or get tech support. They are very knowledgeable and helpful. They talked me through a restart of the iPhone and cellular connection because I wasn’t getting any internet service when I first arrived in Germany (I called them on another phone). (800) 711-8300, outside the U.S. +1 (908) 559-4899.
Other than for navigation we used cellular data sparingly following a model suggested by Rick Steves. In Settings > Cellular disable cellular data for most apps. Turn off cellular data in general or put the phone in Air Plane mode except when you have a specific need. It was handy to be able to do the occasional web search, or translate a museum narrative using Pixter and Google Translate.
Do the majority of your internet work when you have WiFi.