Hi Ted,
I've taken my BB onboard, but I did not have my Wifi-enabled unit until after our last cruise. Basically though, do not use it for calls/texts as the cruise line will kill you with extra charges on your next cell phone bill. If your phone is wifi-enabled, the internet charges are listed in your room's documentation or from the guest services. Most go by a per MB charge, with a varying price range based upon what you will be expecting to use while sailing.
If I'm going to use the internet, I prefer to use my laptop while the kids are sleeping anyway in our stateroom.
I flew to Cambodia in January for a charitable home building project and pre-trip I purchased an Asian package for data on a per week basis. (Rogers). When we went to MK last week, I did the same for a US package, but as we were away more than a week, I did not turn on the cellular until we were safely within the week for data. It worked extremely well since I keep in contact with my client base primarily via email anyway. It did allow me to send the odd cute pic to grandma back home of her grandkids having fun with Mickey.
Depending upon your ports, you may want to purchase a week's international package for when you are at your various ports, but I did not explore them.
Hope that helps.