HI,
I bought a Itead 3G board and had some problems. I found another 3G board by Elecfreaks. http://www.elecfreaks.com/estore/3g-shield.html
I got their board to work pretty much the same software as my SIM900 board by Itead. I have had good luck with the SMS functions. It uses a SIM5215E. Comes with a camera too and about the same price. Haven't had a chance to use the camera yet but will do soon.
StanK