I just received a pair from AudioCubes. With now a couple of hours of burn-in, my impressions are pretty much in line with
plainsong's on page 3. This is a remarkably good-sounding budget closed headphone, one with clear highs and mids rather than the bass-dominated mushiness I'm used to in this category.
Sound quality: nice and clear up top, and I can see how some people might find it strident, though I do not. Mids might be a little bit recessed if I'm listening analytically, but if I'm listening to vocal tracks just for enjoyment, I like the mids juuust fine. Bass is ample in quantity (for my taste) and goes down far enough (for my taste), but has a little bit of an unrealistic, synthetic quality. It does keep the groove going very well without overpowering the rest of the song, which is something I rarely hear in this sort of headphone, but it lacks a little finesse. Overall the headphone has a bit of that "closed" sound of echo/resonance, but that's only to be expected in a closed headphone at this price point.
Isolation and leakage: Isolation, on my head, is modest at best. It barely mutes any outside sounds, though perhaps it'll do better after the foam in the pads has broken in a bit.
Edit: It's not leaky. I was wrong when I said earlier that there was leakage to the outside (I had tried to simulate the effect by covering the drivers with my hands). My wife, whose hearing is very good, said the headphone was inaudible until she got her head right up next to mine. So there you go: good enough for a shared room or the campus library.
Comfort and fit: I haven't had time yet to assess long-term comfort. Short-term comfort is just fine provided your ears aren't the large kind that might feel overcrowded inside the rather small earcups. Clamping force is moderate - neither light (like the K81DJ on me) nor heavy (like the HD25 or the HD280). The headphone is lightweight.
Amped vs. unamped: Really improves with amplification. I'm listening to it now out of a Gilmore Lite, and it's surprisingly respectable sounding. From an unamped iPod Nano, clarity definitely suffers during complex passages. But I still like it pretty well unamped -- quite a lot better, in fact, than most of my portable non-IEM collection, which I won't detail here because it includes at least one Head-Fi sacred cow^h^h^hcan and I'm not up for the flamewar.
vs. K81DJ: I don't own a K81DJ, but based on my recollection of meet impressions (always suspect), I like this headphone much better. My recollection is that I found the K81DJ unclear-sounding and overly bassy even when amped, and and even more unclear-sounding when unamped, and the Pana is much more in tune with my tastes all around.
vs. DT231: I no longer own a DT231, because I gave it away to someone who wasn't as bothered by its bass-dominated sound and mushy mids as I was. But from memory, obviously I didn't like the DT231 much, while I think the Pana is quite decent sounding. The earcup size (again from memory) is about the same.
vs. HD201: I will fill this in later.
vs. ATH-FC7: I will fill this in later.
vs. HD25: The HD25 is by far the superior headphone, but at 3x the price, it ought to be. More convincing realism all around, far more isolation, and more easily driven.
vs. MS-1: The Pana's top-end tizz is what it clearly has in common with the MS-1, and it has a similar quality of drive in the rhythm section, so I can see how the comparison came up. Other than that, I'll have to get back to you.