I purchased my own Verizon LTE HTC ThunderBolt early this year and am grandfathered into the unlimited data plan. I actually paid a significant amount of money to buy the iPhone 4S and keep this unlimited plan. After Verizon killed off unlimited data those of us in the smartphone community warned people with LTE devices that you would eat through your data cap in no time at all. It seems that Verizon is having a slight change in heart now and is offering double date for 4G LTE smartphone owners.
This limited time offer lets you keep the same monthly fee, $30, $50, or $80, while doubling your data allotment from 2GB to 4GB, 5GB to 10GB, and 10GB to 20GB. This should hopefully let you use your LTE device without worrying about exceeding your monthly allotment. I no longer have a LTE device to track how much I use on a monthly basis, but image 10GB would be plenty. You can also add a 2GB mobile hotspot for $20, but I don't see any details of that limit doubling.
Current 4G LTE smartphones on Verizon Wireless include:
Motorola Droid Razr
Samsung Droid Charge
Motorola Droid Bionic
You can always use their data calculator to see how much data you can anticipate using in a month.