If you plan to buy Google's Nexus One smartphone, here's some food for thought: cancelling a Nexus One contract is more expensive than just buying the phone unlocked. Phandroid and others have discovered the phone's Terms of Sale states that cancelling your account not only incurs a carrier Early Termination Fee (ETF) – which is standard – but Google will charge you an additional "Equipment Recovery Fee."
On top of T-Mobile's $200 ETF, you'll have to pay Google the full price of the Nexus One, minus the service plan and the price you paid for the device. For example, if you paid $180 for the Nexus One through T-Mobile, you'd have to pay Google $350 for a total of $530, or the cost of the handset unlocked. Again, that's in addition to T-Mobile's fees.
The catch is that it only applies if you end your service within the first 120 days of the contract, but it's still worth considering if you're eyeing Google's "super phone".