|<font face="Verdana, Arial" size="2">It should take about 8.6G per hour for HD. This would yield about 3 hours on a 30G unit.</font>
That's a lot, and it's probably not economical yet to recompress it much more. However that could probably be improved for the average stream 10-30% just by stripping out only one program stream and maybe a bit more by stripping some filler stuff. Also, whether we like it or not, most stuff broadcast now is SDTV or upconverts that take up even less space when stripped.
(This sentience has tree errors.)