Ok, you can try it. I have read that using it will incur text message charges with Verizon not sure on Sprint.
I would bite the bullet and spend a few bucks on JiveTalk, it's is the best IM Client hands down, it will do all of them in one slick package. Here is the link and you can get a free 30 day trial. JiveTalk uses data only so if you have an unlimited plan knock yourself out! BeeJive :: JiveTalk mobile messenger - instant messaging to go