Well my walnut arrived today, and I did some very brief testing.
a) I expected it to be louder, given the bulk (and what others said), but it's only slightly louder than the C3 I think, I will test more with an A/B switch I have lying around tomorrow. Tested with only mp3 files that were replaygained (mp3gained) to 93db, listened to at max volume comfortably for me, I could go a few decibles louder to satisfy my ears, but I am known around these parts as liking my music very loud (extraordinarily loud), so take that with a pinch of salt. Certainly my AP100 plays same files a lot louder, than I'm sure of (I listen to my AP100 daily and used it this morning).
b) It FEELS light, but is oddly same weight as the C3 (98g), it's fascinating how holding the walnut feels lighter than the more compact C3 (which feels heavy) when in reality they are the same weight just different illusions.
c) The Walnut is hissy, a lot hissier than the C3, although it is oddly not an annoying hiss that I have come across on other DAPs, it's manageable, possibly even a non existent issue depending upon genre.
d) I LOVE how it resumes last place (exactly), and starts up IMMEDIATELY. This is a breath of fresh air in comparison with the annoying non autoresume, non immediate playback, annoying navigation of the C3. I've been using my C3 a lot in the car, and it's a PIA to fire up, I look forward to the instant playing of this, looking forward to trying it out in the car rig.
e) I paid 50% less for the Walnut, definitely good value in my eyes.
f) soundstage feels more narrow, more forward, but in a odd way pretty good and not a bad thing. Separartion and bass control seemed fine (at max volume), no distortion to my ears.
Tested with PFE 232's.
Further testing and pics to come...