I had pretty much the same problem as you with my HD Plasma. I already had Dishnetwork with a PVR and did not want to give up the DVR capability. I had purchased all my equipment and did not want to buy an HD receiver because I was afraid I would be stuck with old technology.
My solution was to keep the PVR and lease a HD receiver. I called up Dish and they set it up. I leased the 811 receiver without DVR and paid the extra 5 bucks per month lease fee. They charged me 50 dollars hookup and gave me the HD package at 1/2 price for a year. I have both receivers hooked to different inputs on the TV. Of course I can only record in standard def, but I can watch one show and record another now. The 811 will decode off the air HD channels and put them right in your channel guide for easy access. When the HD DVR come down in price, I will buy one and return the leased receiver.
I have had DISH for a couple of years and I am pleased. I am considering moving to the HD world and and looking at both DISH and DTV. With DISH, I will need to get a new receiver and have to pay 100 (go figure) What really gets me is if I want an HD receiver with DVR, I will need to buy it ($700+). I was wondering if I set up one TV with the HD receiver and a second on with the DVR, can the two receiver talk with each other of is the only way to get both HD and DVR to purchase the receiver? Neither company is giving me much of a reason to select them.