When using the app on the iPhone (4 and 4S) during online play, it crashes if any player multitasks. For example, if a player tries to reply to a text message then the game crashes for all players involved. Not sure if this is an issue for the iPad.
The ability to multitask without game interruption should be standard.
It would also be very convenient to have the ability to resume games.

Otherwise, the game is well thought out and addictive.

Cheers,
D