So far, I'm pretty impressed. The presentation is very neutral, just like the other NuForce products I've heard.
I'm listening with my (somewhat new) dual-driver Klipsch Custom 3's and it's doing a good job driving them cleanly. Here are some specific thoughts:
The Sound - Dutch Radio Recordings (live alternative, WMA Lossless)
Really brings out the raw nature of this recording, I can hear the different instruments pretty clearly and the nuances of when the lead singer is stressing his voice. The drums have good "slam" but this recording doesn't have a ton of deep bass so can't comment on that.
Strauss - Ein Heldenleben (classical, WMA Lossless)
Decent sense of space, but doesn't really have the same life that this recording does through my other Headroom amp (which costs 10x what the Nuforce does). Nice spread in the orchestra, full range sound. Feels like I'm sitting way back and above the performers.
Air - Pocket Symphony (electronica, WMA Lossless)
Maybe a bit harsh, sounds a little compressed. The synths don't sound warm, lush, analogue-like.
MP3's are actually pretty decent, but I still find myself at lower listening volumes as they seem subtly harsh. Garbage in garbage out...
We'll see if anything changes with more time on the amp and the 'phones. So far, so good but it's no giant-killer. At the current sale price of roughly $90 shipped it's worth having one of these just for the size and convenience and a definite upgrade from the stock headphone connection in the computer.