While there are some homes where there might be only one or two dish positions, I don't think that is the norm. What we are reading is some installation companies are forcing customers to certain mounts only (pole set in concrete for instance) or away from certain mounts altogether (chimney or roof seem to be excluded often.)
I have no problems with installers who correctly tell customers about "there is only one location to put the dish". I do have problems with installers who force customers away from viable installations so they can either get more money or because they are too lazy for certain installs.
The AT9 installation video is clear that you can install the new dish practically anywhere you can install the lighter dishes, so long as you have line of sight. Obviously site specific issues apply: tile roofs, weak chimney, high wind zones, etc. all come into play.
Kingsfan,
The new dish has a larger opening for the mast. There are people working on adapters, I'm sure you'll find them when they are ready. I suspect if the J mount is securely fastened to serious wood you'll be ok. But you might need some stabilizing arms as well.
Cheers,
Tom