Well, over the thanksgiving break, I decided to do some investigation into the DVD/TiVo combo units. As such, I am sharing the results of my investigations so far.
There are two types of dvd combo units: dvd players and dvd writers. There is only one dvd player unit currently (the Toshiba SD-400) while there are two dvd writer units - the Pioneer DVR-810H and the Pioneer DVR-57H. The units share many similarities, specifically:
DVD Playback (including DVD/VCD/CD-R/CD-RW/CD/DVD-R)
TiVo Series 2 functionality, including being HMO ready
"TiVo Basic" service included, with the option for "TiVo Plus"
Progressive scan output (3:2 pulldown)
One USB port
Optical output for Dolby Digital/DTS
However, there are a few differences between the various units.
Toshiba SD-400 (pdf spec sheet)
Street Price: $500
Only has one set of inputs?
After opening up this unit, I was less than thrilled. In short, the unit looks like a cheap Apex-style dvd player and a standard series 2 tivo shoved into a single unit, with slight changes to the tivo motherboard to add progressive output and control communication with the DVD player, and a shared power supply. The dvd player is not a standard PC dvd drive (at least in the sense that it doesn't have an IDE interface or whatnot), and interfaces direclty with a small daughterboard with a zoran chip. From the looks of it, all dvd playback stuff is handled by the zoran board, with the audio and video piped to the outputs directly.
Pioneer DVR-810H and DVR-57H
Street prices: $1000 and $1500, respectively
Faroudja progressive scan output
two sets of inputs (no, not two tuners. as in two sets of composite RCA style connections on the back)
Since these units are nealy identical, the main differences are as follows:
1) regular silver exterior vs. black 'Double-Layered Chassis'
2) 80gb vs. 120gb HDD
3) silver or nickel (not sure) connectors vs. gold connectors
4) one year vs. two year warranty
5) for some reason, the 810 software install is not working with drive expansion currently, but the 57h software is...this is being investigated, could very well be a bug in mfstools 2.0
These units are based on, not surprisingly, the Pioneer 105 DVD-R/RW recorder. The drive inside the unit is the standard IDE based unit, with just a new fascia put on to match the front bezel of the unit. The differences between the units are trivial, and not really something that would be worth the extra $500 to go with the 57H (unless you really care about black vs. silver). The motherboard on the units is very different than any other tivo motherboard I have seen. While some of the differences would be attributable to the addition of the faroudja progressive scan stuff, there are some other major differences (a large pioneer BGA IC right next to the secondary IDE channel). There is also a larger fan than is used on any other tivo I have seen so far, possibly due to the heat produced by the dvd burner. Because the standard PC DVD burner was used, software dvd playback was needed, and apparently provided in the form of LinDVD.