Further research reveals the following with MPD-AP20U:
1. Firmware upgrade for MS Pro Support is there. You can easily use this as a really big flash player given the proper MS Pro stick.
2. Battery life with on-board LiIon battery is about 10 hours. However, the doc has ability to use 8 (8!!!) AA batteries, boosting the battery life to 50+ hours (MP3 CDs. DVD-Video seems to take up much more juice, about 2-3 hours to 20 hours with dock). Official reported hours are about 30 hours for MP3 playback on a CD and 5 hours for DVD video, double layer. Probably more on single layer DVD.
3. It plays MP3s on DVDs indeed, and even on a Double Layer burnt DVDs as well!!
Update: Manual confirms this, plays on anything you can throw at it, CD-Rs and RWs, DVD-Rs and RWs. Manual is inconsistent on this. In one section, it reports that it supports both plus and minus, in others, only minus.
3a. It plays uncompressed PCM 16-bit WAV files as well.
4. One concern: it's picky when burning CDs, and certain users report that it goes bonkers after about a year's time when it comes to reading pressed CDs (but not CD-R/Ws and burnt DVDs...). Strange. It's also a bit flimsy compared to other portable CD units.
5. Unit also supports playlists.
Very intriguing indeed, I'm going to bite on this one.