I've got Directv. While I have a 3-lnb oval dish at home for HD reception, an old (and cheap) dual lnb dish on a fairly ugly roof antenna tripod is a snap to set up when out in the Montana (there are two advantages to using this type of triprod: they are very stable and so ugly that only a desperate thief would steal it). I've been in several wooded sites that required me to move the tripod for a clear view of the satellite. A roof mount would have left me without a signal. As others have said, Directv is easy (at least for standard definiton) because the signals are all from one satellite. The satellite finders (signal meters) are a must. They're at CW, but can be purchased for less on e-bay. The meters don't differentiate between satellites, so that after getting a hit on the meter, you need to view the satellite signal strength on your TV. The Direct and Dish satellites are in the same area of the sky, so you'll often hit the wrong one.
Here is an excellent guide to satellite TV with an RV:
http://www.ccis.com/home/mnemeth/sat.htm