Er, you understand that car adapter mode simply puts the playing player into pause when it is disconected from power, and then simply starts the player again when power is reapplied (assuming power is in fact reapplied--otherwise, the player shuts off in a few minutes), right?
I don't know that I would choose a player for that feature, but I guess we all have certain needs.

Note that car adapter mode was causing iRiver Hxxx and other players to freeze (requiring a hard reset) in last month's builds and builds from mid-May or so on (there are 2 bug reports on this)--I haven't heard that this has been fixed, yet (but I also haven't updated the firmware in 3-4 weeks or so).