Here's my conclusion:
If you want an iPhone and actually use it, Sprint has the best deal.
If you want an iPhone so you can say you have an iPhone, Att has the lowest price(, 450 minutes, 200mb of data, and no text) at around $60 for pretty much nothing but email abilities and talk time.
Sprint only has unlimited for texts, while Verizon goes down to 2gb for $30, and Att goes down to $15 for 200mb's to help people in debates of which is cheaper.
Sprint has the most expensive up-front talking plan, but it also includes texting, and free mobile-to-any mobile talking. This is only $10 more than the next closest from Verizon's $59.99, which also includes texting.
To me, it's pretty clear. If I had an individual plan, and was looking for a new contract to full utilize the capabilities of my iPhone, I would go to Sprint. However, I'm on a 4-phone family plan. Sprint is an expensive alternative for family plans, as is Verizon. Att is clearly the cheapest in this category.