My concern is the "weight" of Linux.
I have two PVRs. One is an "iPod recorder" built by Unisen in China, the other is the Neuros OSD. Both contain the same core - a TMS320DM320, along with AIC23 for sound and TVP5150 for video. The Neuros has multiple card readers (SD, CF, etc), ethernet, and numerous "features" including a choice of audio codec (MP3 or AAC), and different video quality from 256kbit (ho ho) up to 2500kbit (damned near DVD quality). It also looks good on-screen. The Unisen box looks pretty icky on-screen (very obviously low-res-ish bitmapped). It is pathologically fixed to record everything at 30fps and spit out NTSC. It works "acceptably" with 25fps PAL, but proper support would be better. You can, like the Neuros, choose the image size, but the quality level is fixed (approx. 800kbps VBR as far as I can tell).
So obviously the Neuros is the winner, right? I really like my OSD, and with my screwed up work hours I rely on it a lot.
But, hang on. While the resultant .mp4 identifies the core video library to be the same, and I can't imagine there are that many places you can get NDA-locked DSP code, there are enormous differences in the firmware. The Unisen runs what appears to be a custom monolithic system in (I think) 8Mb FlashROM. To be honest, it looks it could be a reworking of the sort of thing hat might be supplied with evaluation boards. :-) It is simple and to the point. The OSD is also simple, to use. Bright and clear menus, it runs a hacked-down Qt4 Debian from CF card, having outgrown the 16Mb Flash. I can telnet into the box to "df -h" to see easily how much space I have left. I installed dosfsck to keep an eye on my devices, for I don't feel I can trust Microsoft to look after their own disc format.
Then, the truth. The Unisen box boots from power-up in around twenty seconds. The OSD takes closer two minutes. Press REC, the Unisen box starts recording in about four seconds. The OSD takes around 16-20. On the Unisen box, pressing Play during record toggles between a blinking red thing in the corner, or full overlaid info. It does this instantly. Pressing '?' for info banner on the OSD can take up to 8 seconds.
I can see many benefits to a standardised operating system, it can span differences in phone hardware, it can offer faster development times than building something from the ground up, plus enhanced security through a long history of peer review and development.
Perhaps what we need is a severely cut down and reworked Linux aimed specifically at the needs of lightweight devices? I'm sure there are many design decisions that make perfect sense to a solid hardcore server, but which may not translate as well to a little 200MHz ARM powered video recorder that can fit into the palm of my hand...