Most movies are 1080p @ 24 frames per second, while sports programming is 720p @ 60 frames per second, so most content is not 1080p @ 60 frames per second. The heaviest broadcast content out there is 1080i @ 60 FIELDs per second, which data wise is only a little bigger than 1080p @ 30 frames per second.
Of course, games can be 1080p @ 60 frames per second, and the LinuxMCE UI is at its best at 1080p @ 60 frames per second. And these might not look their best after being compressed to a 4.7 GB...
Note also that the HDTV on cable and satellite is heavily compressed, so there is little point in trying to use a low compression ratio, it will never look as perfect as a well produced Blue-Ray or HD-DVD disc. Over-the-Air broadcasts are less compressed; but thanks to a lawsuit the EFF won against the FCC, you can record those directly without this type of device.