I know it uses more space but still it uses less space than MPEG2 HD. I have 3 hours of HD content and it is only using about 2 hours of space out of 30 hours for HD content.
according to the csr i spoke to a day ago, all hd channels are mpeg 4. When i said i had a hard time believing it he said 'don't worry i am sure of it'. I still think he was lying.