Watch the contract pricing language closely. Some of the discounts they are offering may only be for the first 6 or 12 months of your service. After that, price goes up. I know that going in but still sucks when the increase happens.
There's probably also some very fine print somewhere that says, "We reserve the right to change/add to/subtract from/charge more for this contract at any time we want without notification, however YOU are locked in to whatever we say you are locked in to (which is also subject to change without notice)."