When you are off-contract, you DO have way more leverage with Sprint. Take the airave for example. If you're fresh into a 2-year contract, and you have bad reception in your new house/apt, you can ask Sprint for an airave. They will be less inclined to give it to you for free because they know you can't just leave (ETF). But if you're off contract, you can threaten to jump ship right then and there. And then they will give you the airave for free.
I speak from personal experience. In 2007, I was off contract, and I got the original airave for free after I threatened to leave (why should I pay more $$ just to get basic air coverage?). Now that I'm in the middle of my 2-year contract, they refuse to give me the new airave, even though I'm using the same argument. To Sprint's credit, they offered me $50 off. But I'm pretty sure it will be 100% off if I had the leverage to just terminate my account.