We dropped txt about 2 wks ago
My wife has a Cappy and I, the Infuse. That means more chat clients than there are stars in the sky to choose from.
SMS/MMS is so '90's now.
Plus geting back $20 a month...WIN!!!!
EDIT: BTW, you can tell AT&T to block all incoming/outgoing SMS/MMS to your number, so if anyone tries to send you a SMS, it's blocked and you don't get charged.
Need to send SMS? Google Voice, Skype...the list is long.