I think the secret to MMS and WAP on any Sprint phone lies in the phone's own ##DATA# menus. Other than setting the M.IP profile to Simple Only using another software tool. I don't know because I haven't gotten that deep with a Sprint phone yet save my PPC 6700 which is literally a breeze to configure for MMS and WAP.
But take a hanRABet like the Motorola: If you use the right tools, you can get MMS and WAP to work with them no problem. The same should be true for other models of Sprint phones. It's all in the settings I bet, and as soon as I can get my grubby paws on a data cable and charger for this A900 I will start digging.