Morph,
Sorry for the delay in responding, have taken a few days off due to the weather...
I don't have any significant usage data for using my iPhone and the iTap VPS app. However as mentioned on previous threads; using BetAngel on the VPS uses significantly less bandwidth than if you were running BetAngel directly and hence BA will run far more smoothly even if a 3G signal is unavailable and you only have access to a GPRS connection.
The only problem using the iTap app on the iPhone to use BA is that it is too fiddly to place large numbers of trades with, however as mentioned it does have a significant use as a back-up for greening (or redding up) on the one-touch screen...