Just to reiterate, if anyone else out there is considering switching to DirecTV, make sure that you do it through their referral program. You'll get $100 off, as will the person who referred you. All you need is an existing DTV customer's account number, which I (and many others) would be happy to provide.
You can't add it after you've signed up, so make sure you sign up through the program in the first place.