Ummmm.....I'm not going to comment on whether it sucks or not, but I would like to point out that I think you guys are sort of misunderstanding the application of this device. While it IS an amp, and it does drive headphones, it's NOT a "headphone amp" in the sense that anyone on head-fi typically uses the term. It has no tuner, no electronic input of any kind, just a built-in mic.
This appears to be a device for people who are trying to listen to, say, their overly quiet teacher in a giant lecture hall, or people who are trying to listen in to their roommate's whispered telephone call, or something along those lines (depending on whether you believe in the intrinsically good or evil nature of the human spirit...). I would presume that the 150-10000 Hz range is intentional, since you wouldn't want to amplify the LF hum of HVAC equipment, or shrill sounds above 10K. Although in the description, they mention listening to TV without bothering those around you, that seems like a bit of a stretch. I guess it would work, if you didn't have, say, a long headphone cord, or wireless headphones, or whatever, but it's not designed for hi-fi. We're basically talking about somethinghis designed for targeting the human voice.
Different goal...different specs. That's not to say that it might not suck for that application, since I haven't tried it (and have no desire to), but an AirHead it ain't.