You might want to check things out first and see if the new shared plan will save you money or not. Go to My Verizon on the web, and check your data usage for the past 6 months. (Check past bills). Add up all the data usage, then check the price of the next highest level of data plan. Add up the prices of the phones that you have and you will have what it will cost. Compare that to the cost now (make sure that you either remove the fee price from your current bill, or add the fees to the new data plan price).
For me, if it was just the 2 lines (wife and myself) I could save money. But adding in the new expensive price of the 2 dumb phones for the kids likes (yes they are old enough to have their own phone, one is in law school, the other unemployed at the moment). and the new plan will cost me money.
Second thing to consider, coverage. Yes Sprint has unlimited, but how is their coverage where you live, where you work, and where you travel? If their coverage is spotty where you use the phone the most, what good is unlimited data when you do not have a signal?
Not saying to stay or go, but check it out first. I don't have to make a decision for my situation until next year when my Galaxy Nexus comes up for replacement. I do know one thing. My Galaxy Nexus is a LOT less buggy without the skin of any of the manufacturers. My Droid X has some bugs, but it was a LOT more stable than a lot of people with the same phone. I was happy with it, in fact, I will have it and use it for testing.