CasaDelSol,
I have Directv with the HD Receive and have installed a Winegard SK-3005 dish on our 2955RL. I have carried a Slimline 5LNB tripod setup along just in case. I can tell you the way we travel I have had only one place in our trips where I could not get locked on to the satellites with the roof top dish. This was in Oregon (LaPine)in heavy trees. I have been amazed at how well the roof top SK-3005 can locate and lock onto the satellites even in trees. I have locked onto satellites where I know I would have had a problem with the tripod. From now on I will leave the tripod and Slimline at home.
You can view my installation at
http://www.jolusspot.blogspot.com/.
Installing a roof top dish on the 2955RL you can route the coax and power right into the top cabinet over TV and down into the cabinet below the TV.
An internet search for the SK-3005 will probably produce prices from $1350 up. So the price depends on if you go with DTV HD or standard tv.
One can also make a simple satellite pointing devise which can make locating the satellites much simpler if the tripod method id used. Also there are several programs you can download free that will give the coordinates and skews of the zip code you are in without even turning on the receiver.
Good luck with your decision and happy travels.