I have a 160 gig hard drive that is full of video, both mine, and rented. I find that it fills up very quickly. I use DVD Shrink to “re-author” the DVD. I strip all of the extras, and then trim the start and end of the movie, that way I get the least compression that way. Usually around 97%, this is good enough for me.
I then burn the rented copy to a DVD-RW for time shift viewing. I have three RW disks that I re-use, and once I have viewed I delete the source from my hard drive.
I know that disk space is cheap, but it seems to fill up very quickly with video projects, so I question the value of putting my entire DVD library on disk. They are not MP3’s yet.