Pros: I have used many other portable and desktop headphone amplifiers, I've even built my own amps. But there's no way I could build anything this small. I enjoy the little bit of bass boost it provide when listening. Having to unplug headphones to turn it off seems strange at first, but it's really easy when you're carrying it around in a pocket.

Cons: There is audible hiss when used with low impedance earphones, generaly it's not audible, but in quiet sections of music I can tell it's there.
The cable that came it is poor quality, I could hear it degraded quality and I had to find another.

Other Thoughts: It goes through AAA batteries pretty quicky, so get some Nimh rechargables.

Bottomline: I enjoy using it with my Sansa Clip.

Pros: This thing is great. It causes a vast improvement in the overall sound. I don't know the inner workings, but I can say that I haven't heard even the slightest of hisses or pops caused by this. You won't find any. This is a quality product.

Cons: The only real cons I can see in this are those additions made in its successor. The battery isn't fun to replace too often, though it does last pretty long. There is no off/on switch, so if your headphones are plugged in, it's on. There's no volume control, so on many things it does end up being too loud. Overall though, it's great.

Bottomline: If you can't afford the latest version, this will do. It sounds great and it really does improve the experience.

Pros: nice.
i bought a couple to try out and i'm glad i did.
it really does work as good as the others have said. it's really tiny.
at first i thought it wasn't such a big deal. but the more i listened to it the more i like it. there's not an enormous boost in the sound but it does amplify it. i didn't notice what a difference it was making until i unplugged it and used the earphones by them selves. OMG! they don't just boost sound, they boost everything. what ever brand of earphones you use. this thing will make them sound better.
it'a a sound quality booster. more bass, crisper clearer treble. if your device has preset equalizer settings it enhances that too.
it even makes some really shytty earbuds that came with some junk fm scanning radio i got for a $ somewhere sound better.
no, they didn't transform cheapies into a $100 pair but hey did make them tolerable if your in a pinch. [like if my fat dog chewed up my good pair]
it's just barely bigger than a aaa battery.... actually it's the size of two side by side together. it only runs on one aaa though.
i think the best part is that it saves battery power in your device by not having to power the earphones. it added a few extra hours on the runtime of my mp3 player. i don't know how long the battery in it will last before needing changed because i havent run the first one down yet. after 5 or 6 hours of trying it out with different head phones and on different devices it's still goin' strong.
a jack to jack jumper wire is included.
it comes in a very nice box with a decent user manual and a minimum amount of "engrish".
neat litte $7 gadget.

Cons: 3 cons
1. no on/off switch.
2. no seperate volume control.
3. no by-pass, when the battery is low or dies.
you will know when the battery is dead, it quits, and no sound goes through it.

Other Thoughts: i really like it. i know i'll need to buy more.
i can't stand to listen to my tunes without it now.
sounds great with a pair of genuine ipod earphones, not the $2 imitations. [they sound a lot better with this too]

Bottomline: if you listen to music through ear/headphones get one of these.
it should be a law that all ear/headphones come with this amplifier!

Pros: This amp will give you a really good bass-boost, if you have apropriate headphones (the sku.3396 will do really good). It has overall volume increase and good bass increase at most (really good for bass lovers). Extremely easy to use.

Cons: Could use on/off button. The plastic is a bit frague. Does not work with all setups. For example my big headphones have almost no difference with this on, it seems that does not improove the quality much for good headphones, expecially if connected to a good PC sound card. It will, however improove the quality of the sound if your big headphones are connected to low-power input.

Other Thoughts: 2xAA batteries sized, indicates when it's on via led. Not good to amplify loud sources.

Bottomline: Buy this one to enjoy more bass tests with apropriate headphones/earphones. Generally boosts bass and it boots a litle bit the overall sound. Seems that it has good battery life.