BGAs suck. I had to replace 2 wireless G usb cards because they got warm or my house is warm and they got loose and are half way off and burned out. They SUCK! excuse my language. I rather do a 100pin QFP then a BGA
From WIKI:
"A disadvantage of BGAs, however, is that the solder balls cannot flex (non-compliant) in the way that longer leads can. As with all surface mount devices, bending, due to a difference in Coefficient of thermal expansion between PCB substrate & BGA (thermal stress), or flexing & vibration (mechanical stress) can cause the solder joints to fracture."
I would never use them and frown on companies that do.