I'm thinking of buying another DVR either the 508 or 721 but this whole mpeg 4 thing worries me I Don't want to buy it now and have it where I can't use it in a few months or a year when they change to Mpeg4 and it would then become useless correct? Should I wait until Mpeg 4 rolls out until I buy another DVR or will they upgrade the one I buy to a current one when they do change formats or will I be stuck with something that is just useless and have to buy a new reciever? I want another one but am worried about the Mpeg 4.