The Tivo_Zipper script will preserve your recordings as far as I know. TivoServer will stream VOBs, but I never tested that function myself. The problem with using a DirecTiVo as a media streamer is the lack of support for anamorphic widescreen output. I am currently using a quiet SFF PC running Media Portal. I have only been using it for a week, but it seems to work very well for the price (free).

On another note, I heard an estimate that MPEG2 SD streams would be available from DirecTV for at least 10 more years. That wasn't official word from DiecTV, however.