[mackmgg]

It supports an ACK, but unless you have a two-way i-gate nearby you should probably consider it to be a one-way protocol. All of the ones near me just go RF -> internet so there's no way to get a response back to RF unless you're running your own.

Still useful for sending out quick status updates like "I'm doing fine but running late" but not good for full blown communication.

[twothamendment]

Exactly this. My wife knows not to panic if she can get my messages, but I don't reply to her. If any hams live in an area w/o a two-way i-gate, consider putting one up. It isn't that hard and provides a nice service.