I'm planning an installation of a High Def DirecTV sattelite system. My house is pre-wired with RG-59U cable. The desired location of the receiver/TV is on an interior wall which does not allow for fishing cable. I would like to run RG6 from the dish to a point in the attic where I can connect it to the existing RG-59U. The RG59U run would be about 30' with no splitters or other devices. I have not yet decided which brand receiver to use, since the choices are still very limited.
Does anyone think this will/will not work?

Can you pull RG6 through the interior wall using the existing RG-59U cable? I guess what I'm trying to say is. Avoid the RG59-U if you can. I have a friend that did what you are thinking of doing. It is working ok. I however have no idea if it would work with a HD receiver. Good Luck.

In my earlier, more naive days, I wired my entire house with RG-59. I have now had the opportunity to replace all of it with RG-6. Go for the best RG-6 you can lay your hands on, preferably with factory connectors. Radio Shack sells good RG-6.
Futhermore: as long as you're going to the trouble, I'd install a multiswitch in the attic, which allows distribution of the signal to mutliple rooms without signal loss. The RCA Oval dish comes with a 4x4 MS, but you buy one where you can also connect an antenna, and send a combined antenna/ DSS signal to multiple rooms. WHY AN ANTENNA? To get local HD broadcasts, of course! I use a TERK TV55, which works fine if you mount it outside. See www.gohts.com for further advice.