Had the Pandora for a day, here's some first impressions.
When I first plugged my headphones, I thought the detail was slightly reduced compared to my Playstation Vita, which uses the Wolfson WM8973G DAC. Some notes on a dense song I listen to appeared to be melding together. This was very discouraging.
This was psychoacoustic. The song (Technocracy by Psyborg Corp) is just stupidly dense. Plugging back into my Vita and doing direct comparisons revealed this to me. The melding was actually worse on the Vita. The synths have more texture on the Pandora and as I have never heard this before, my ears were tricked.
Using my favorite portables, the Beyerdynamic DT1350s, the Pandora is able to deliver a ridiculous amount of bass slam and power. The tactility of the 1350s really shines through on this unit. The highs have more sparkle and extension than I'm used to hearing from them. I honestly have never heard the 1350s sound this good. Additionally, my KOSS Pro/4AAAs sound much better out of the Pandora as well. They lose their slight forwardness in the upper midrange on the Pandora, and the soundstage expands. They have a performance-like quality to them, and the Pandora delivers it better than my other sources can.
The amp section is quite powerful. It gets my SE-700s louder than my E7 can. The SE-700, for those who don't know, is piezoelectric, and is ridiculously insensitive and has technically infinite impedance. It's by far the hardest to drive headphone I own. It doesn't sound very good out of it, no, but at the same time it doesn't sound good out anything but my home rig since it's so insensitive.
I have not been able to get the E7 working with the Pandora via USB yet. I'm still working on it; I'm pretty sure all I need to do is attach it to a USB hub, as that's the solution for most USB-HOST related problems with the unit. Unfortunately, I don't HAVE a USB hub; I'm going to pick one up from the Dollar Store tomorrow if possible.
A few comments about usability on-the-go. The Pandora is not very large; I have no problems getting it in or out of my jeans pocket. It is thick however, and while it's not uncomfortable I do feel that it's there. I'm concerned about the shoulder buttons, as they are flush with the system and I foresee them getting pressed by accident while the unit is pocketed. The volume dial and headphone jack are on opposite corners of the unit, which could present a problem if you have it in your jeans pocket and have to adjust the volume. I have not actually taken the unit out yet, so this is just what I'm guessing.
One thing to note is that there is not a line out jack on the unit. I was mistaken, the EXT port has pins for a line out jack; the cable needs to either be purchased or constructed from scratch using the connectors available from the online store. The same is true for the TV-Out cable.
So far I'm very impressed with the sound and the device itself. I'll continue listening to it and report back later.