It's supposed to be for incoming messages from an exchange server only. I get a few non-Exchange related messages (less than 10 a month) and occassionally send a message or two a month, and they have never charged me.

I suspect it will work like the EN-MOU thing. Eventually, people will abuse it and they will start putting tighter restrictions on it or take it away. Then there will be tons of posts from people complaining they were able to send and receive for free but Verizon took it away.