It was spotty for us as well on the Fantasy a few weeks ago. We had a mix of phones in our party - 5 iPhones, 1 Android (not sure of the model of phone), and 1 BlackBerry running the Android version of the app.
We did experience a lot of very delayed, and out of order, messages. You'd get a "We're headed to dinner" message on time, then two hours later, get that mornings "We're headed to breakfast" message from the same person.
- The iPhones seemed to work the most consistently, but they didn't get many vibrating notifications.
- The BB running the Android version of the app worked pretty well and got the vibrating notification intermittently - maybe half of the time. The BB supports Android apps, but usually not very well, so it was a nice surprise that it worked at all.
- The Android seemed to have more of the delayed messages than the others (then again, I probably chatted with him the most often, so it had more opportunities for delay). I didn't hear if his got the vibrating notifications or not.
It takes a bit of work to set up especially if you have a lot of users in your party, but nothing that we felt was overly complex. To add someone you need to know their unique ID. When you open the app, you are shown your unique ID. Once you have that, you need to tell it to the other person, they enter it and start a chat, then you are connected for the remainder of the trip.
The suggestion above to do all of that in the terminal is an awesome suggestion. We didn't know about the unique ID thing until we were separated and had no way to contact people.
It would have been nice to have an "Add a cabin" feature where you could add everyone in a cabin with one unique ID code.
Lastly, a Group Chat feature would be a great add. We had 7 people spread among 3 cabins on our trip. It would have been great to message them all with a single message as often, we were split into small sub-groups on the ship.
It definitely needs some work, but overall, we felt it was much better than nothing at all.