I've always gone with the no-contract plans. I pay $35/month for the same phone and unlimited service that one of my family members is paying $100/month for. Really I don't see the point of the contract plans.
For example Straight Talk, is 45$ / month, everything unlimited. And you can use either AT&T's coverage, either T-Mobile's or Verizon's (and their phone too).
And that's for everything unlimited, you can find cheaper if you don't need unlimited.