My wife has a Treo 300 and I have a 600. Now with Sprint I can send her SMS messages, and since downloading a trial version of SMS Treo 300, she can send me messages. When she sends a message, it goes through the Sprint Vision network, but when I do with my 600, it doesn't need to connect to the Vision network. Why is that? Can she use SMS on her 300 without accessing the Vision network? Another thing I'm wondering is if there are any charges to either of us when we send messages because we're being charged for minutes, etc. We do have "free" pcs to pcs minutes on our plan, but I'm still curious about whether there are any charges for messaging in general.