I just bought a Panasonic DMR-E55 that records on DVD-RAM's as well as DVD-R's: while I'm still getting the hang of it, the DVD-RAM seems to have some of the benefits of a hard drive (I also have the hard drive-based Tivo).
I imagine differences in the two formats will become clearer as I gain more experience. The E55 was $350, while the Panasonic 80H Josh mentioned is $699? (Best Buy had an open box 80H for $399).