Well, got back from some 20 hours of travel time over the Thanksgiving holiday. Flew from Austin, TX to Houston, TX to New York, NY, then took the train from Port Jefferson, NY to New York, NY to Washington, DC, and then flew from there to Chicago, IL to Austin, all to test out the Karma in these most rugged of conditions!
I re-ripped all my CDs to Vorbis over the course of a couple of days using the Rio software, and converted my iTMS music to FLAC using other stuff. It was fast and easy, and I have no complaints. The UI is a little weird, but once you figure it out, you're okay. It'd be nice to actually say what quality level each Vorbis setting is (is "best" 5, or 6? 6 would be nice for the discrete stereo).
Battery life and physical usability was great. The player finally crapped out about halfway through the flight from Chicago to Austin, after easily fourteen hours of travel time. The nipple and the wheel and the lock were all easily manipulable without me paying much attention. The unit was plenty loud, although my noise-cancelling headphones probably helped a bit, there, and I didn't try it without them.
Complaints? I'd like to see Replay Gain tag support in both the Rio software and on the Karma. Having to turn the volume up and down sucks, and having to run VorbisGain on all my freshly ripped audio files also sucked.
I'd also like a few preset auto-generated playlists. Like "Play All Music" and "Play All Music Shuffled", since switching shuffle on and off is awkward going through all the menus, and having fresh rips means I didn't have any playlists at all.
It might also be nice to have an option to shut the LCD off entirely after a few minutes. Could save a little battery life, and on a long trip where you pick a playlist and stick with it (and aren't staring at the screen), you don't need it scrolling the song titles forever.
I'd also like some sort of case or screen protector. It's pretty scratched up now, and it was almost exclusively in the pockets of my cargo pants. Not exactly the roughest of containers.
Now all I need is a couple extra docks and AC adapters, a remote, and an aux input for my car stereo.