the older hr10-250 hd tivo from directv does not output sd/480i (to the dvd recorder to record)and hd component/hdmi (to the tv to watch in HD) at the same time. not sure if the new hr20-250 hd dvr or H20 HD receivers do this or not. there is a hack to get the hr10-250 to output over sd and hd outs at the same time though. check the tivo community underground/upgrade section.
the Tivo S3 hd dvr does output both SD/480i (svideo/rca) and HD (hdmi/component) from it's outputs at the same time so if you had one of thise you could send the SD out to your dvd recorder and the HD to your tv and watch HD while your dvd recorder was recording SD. With the hd dvr you could record and watch later or send SD copy out to the dvd recorder whenever you wanted.
the Tivo S3 hd dvr does output both SD/480i (svideo/rca) and HD (hdmi/component) from it's outputs at the same time so if you had one of thise you could send the SD out to your dvd recorder and the HD to your tv and watch HD while your dvd recorder was recording SD. With the hd dvr you could record and watch later or send SD copy out to the dvd recorder whenever you wanted.