Alternate (that works) is drop your data plan from $25 2 Gbytes to $15 / 250 Megabytes, and go buy a $60/Month Sprint MiFi/5 Gigabytes (Wireless HotSpot).

Total Net Cost is $35/month above what the iPhone normally costs. $60 (Sprint) - $10 (Data Plan Savings) - $15 (Tethering Cost)

The net costs are less if you have an iPad AND an iPhone, as you don't have to purchase a 3G iPad or a Data plan for it.

Advantages:

  o Data Limit is 5 Gigabytes instead of 2.
  o iPhone, iPad, Laptops all can (simultaneously) use it.
  o You now have Sprint and AT&T Data Coverage.
  o All of the "WiFi only" rules work on the MiFi
    (Facetime, AppStore download Limit)