I just got mine yesterday from Micca Store through Amazon. Although I wont be using the amp for quite the same thing as most people, I'll go ahead and post my opinions anyway.
I have to first say that I wouldn't really consider myself and audiophile (yet), and I don't own any high quality headphones (again, yet; I've bean reading a lot on the forums here, and I think I'll be getting some ATH AD700s later in the year). Anyway, I'm using the amp to connect my headphones to the sound output on my video game consoles, as my TV doesn't have any headphone ports. I used a male 3.5mm headphone to double female RCA to connect the sound output from my Wii to the amp (and I keep the amp plugged into the Wii's USB port while using it so that I don't have to worry about batteries).
I tested the amp with several games and it worked great. The sound was crystal clear and there was no hiss unless I turned the volume up quite a ways, well over comfortable listening for me. I've tried it with all the EQs and I have to say that I liked the sound best with the EQs off. Though I did think that EQ 2 sounded good for games with an orchestrated soundtrack. The only negative I have is that twice I have heard a high pitch sound from my headphone; both times I made one full cycle through the EQs on the amp and it went away. I did try the amp with my Sansa Fuze (I have Rockbox installed), and although it didn't sound bad, I felt that it sounded better when I just plugged my headphones directly into the player. I should note that I haven't really used the amp with the Fuze much at all.
Over all I have to say I'm immensely satisfied with the sound quality of the amp. I've never heard my video games so clear; I've heard sounds I had never heard before, and it would sound even better with a good pair of headphones. I should also note that the amp felt well built, despite being very small and light. The wires that came with it also felt very sturdy, and the clips feel very strong.
I know my impressions probably won't be useful to most people because I'm using it for a different purpose than most, as well as not being very experienced in hi-fi sound, but I thought I'd give my two cents worth anyway.
I do have to say I highly suggest purchasing from Micca Store. The shipping was very fast; I ordered the amp on Monday, it shipped on Tuesday, and it got here on Thursday (and that's from Virginia to south Florida). The only issue I had, and it's minor, is that the free headphone splitter that came with the amp wasn't the best of quality. I could get my headphones into one of the jacks easily, but the other took quite a bit of force; when I tried to remove it, the headphone jack pulled out of the plastic guard surrounding it. This wasn't a big deal though since it was free, and I didn't really have a need for it.