I have tried a number of in-ear phones and have been left disappointed by them all, finding them too uncomfortable to wear for a period of time to justify the superior sound quality over the standard earphones provides by Apple. With these reservations, I plugged the S4i's into my iPod touch with low expectations, and initially my prejudices were confirmed, with the standard rubber inserts being uncomfortable and sound quality poor. However, with a little perseverance and experimentation with the other size inserts provided, I found a set that fitted perfectly and could enjoy the excellent bass and range of these little wonders.
Hip-hop, Jazz, Folk, Dance, Rock, Classical: the sound quality was superb no matter the genre of music I threw at the S4i's. (An added bonus is that the snug fit blocked out all but the noisiest of external noise, so I could have the volume low whilst still blocking out the terrible Musak during a trip to the shops!)
Also included is a clip to fasten the the earphones lead to a lapel giving you easy access to the inbuilt controls and microphone, wax cleaners(!) and a handy pouch to keep everything stored away tidily when not in use.
All-in-all, I'm extremely impressed with the Klipsch S4i's and now consider myself a convert to in-ear phones. Highly recommended.