I appreciate people's pictures... but I am really looking forward to reading about what people are hearing.
In the last week I have done a fair amount of listening to the Pico Power, typically a Lavry DA-11 as source, but sometimes an AQ DragonFly, and occasionally taking sound directly from the headphone jack of my iPhone. Music is nearly all loseless 44/16 though I have a few higher resolution tracks. I have been mostly listening to HD800, though I have tried Westone 5ES and Etymotic HF5 IEM. I have been very impressed so far. There have been no glaring flaws in the Pico Power which is pretty impressive given it's price, size, and battery power. Tonal balance is neutral, reminding me of my Headamp GS-1. I had no problem driving my HD800 to high listening levels with the gain set to medium. The amplifier works well on low gain for the IEMs. I am pretty sure I have gotten more than 20 hours on the first two sets of disposal batteries but I haven't been keep close track... my rechargeable batteries arrive today. Channels are well balanced even at low volume levels. I hear no noise with the HD800, and don't hear noise with IEM until the volume is turned high enough to damage my hearing if music was playing.
Bass: clear and controlled. The speed similar to the GS-1 and detail is close, though the GS-1 seemed to have slightly more weight / impact. It will come as no surprise that it's not at the same level as the GS-X mk2.
Mids: Fairly smooth but with a bit of grain, good level of detail, a bit lean in the lower-mids? Depending on the track it seems to be the GS-1 equal, sometimes the GS-1 seems a bit more refined. GS-X seemed a good bit more refined.
Treble: Crisp without being glaring. At the very top end there seems to be a bit of a roll off compared to the GS-X. Sometimes I though it was the GS-1's equal, and sometimes it didn't depending on the track.
Sound Stage: Smaller than either the GS-1 or the GS-X with less air. This is what I most quickly noticed listening to the Pico Power.
Summary for me: A battery powered amplifier which drives the HD800 as well as many desktop amplifiers I have listened to and completely blows away the amplifier found in every USB power DAC/Amp I have heard, and the few battery powered amplifiers I have tried (my experience with other battery powered amplifiers is not extensive). On lesser tracks I sometimes couldn't tell this difference between the Pico Power and my GS-1 in blind A/B comparision. With high quality sources it becomes clear that while the Pico Power it's not quite a battery powered GS-1, it's pretty close, and I like it more than the Gilmore Lite. The Pico Power is good enough for me that I will no longer feel compelled to haul around a wall powered amplifier when I want to listen to the HD800 outside my living room. I am not even going to bother with desk amplifier in my office anymore. When I am not 100% focused on music, the Pico Power is good enough.
