I can. My family plan is over $50/mo cheaper with Sprint *and* I have unlimited data to each of the 3 iPhones on my plan.
Yes, I switched from Verizon to Sprint for those exact reasons.
+1. Three 4s phones on Sprint because of the ability to share an unlimited data plan. If the monthly rates on data phones go any higher everyone in the family will get a cricket phone and learn to live with it.