Pros: Lightweight, good-looking, isolation, nice sound when the right spot is found, cost-benefit
Cons: Need of "ear tuning", annoying cable sensitivity
I think the S3 nails a very intermediate niche. People who's coming from cheap $10 earphones or those awful Apple sets would be blown away by the sound coming from this piece. But those who are coming from the "audiophile" side and are somewhat used to high-quality headphones of any kind would listen to it and think "well, they are just OK, but I'll take them, I need a good portable option". The Klipsch Image S3 is the Sennheiser HD201 of in-ear headphones, which means an awesome cost-benefit. For $30 you probably won't find anything better than this. Crisp mids and highs, a good dose of bass, decent soundstage, great isolation.
It comes with 3 pairs of different silicone plugs, so you can choose those who fit or sound better. In my case, only the bigger ones gave a good fit and bass, and still I needed to search for the right spot through my ear canal. Once found, the sound turned from an awful, hateful, tinned no-bass-at-all sound to an above-average, expanded sound with plenty of bass. So, if you buy one of these and gets horrified at first listen, calm down. Choose the right plug and find the right adjustment to your ears, you will be rewarded.
One bad thing is the cable sensitivity. When it touches something or rubs at your clothes, it will give a somewhat annoying interference, just like tapping on a live microphone. Well, nothing's perfect.
If you're looking for some high-end in-ears for everyday mobile use and have some more cash, take a Shure or Ultimate Ears. But if your budget is limited, take the Image S3. They're much better-sounding, ear-fitting and stylish than any cheap earphones, and comes with 3 sets of plugs and a little case. I'm enjoying mine, and probably I'll like them more after some time.