My DH has one. It sucked at WDW!
It was fine last Sept when we were just using it to check wait times and play games. But when we went in November and FP+ had just come online, it was pointless. The internet wasn't fast enough to change FP times or even load half of the time.
At the same time, we talked to several CMs that week and they said that non-tracphone phones were having the same problem. There were MANY complaints. Hopefully, the whole system is a lot better now, but somehow, I doubt it.