While the back-end seems to have stabilized in the past few months, I'm not sure how useful it'll be unless/until is integrates with both iMessage and SMS/MMS,

While the back-end seems to have stabilized in the past few months, I'm not sure how useful it'll be unless/until is integrates with both iMessage and SMS/MMS, even if the latter requires an iPhone to actually send and receive messages, and until it does at least "eventually perfect" conversation synchronization between devices.