Stunning! Night-&-day difference compared to other in-ear headphones, although you must be patient & take a little time to experiment with the various-sized earbud tips (included).
Very detailed sound that has surprisingly deep bass (where & when appropriate), clear & punchy mid-range with refined top-end treble. It's well-worth adjusting your iTunes Import Settings to Apple Lossless, because the X10s will dig out the extra detail - & they'll expose the inadequacies of low-bitrate (MP3, AAC) formats. IME, X10s also suit all genres of music - from Bach to Bowie, Mozart to Massive Attack, Chopin to Coltrane.
Build-quality is 1st-class, but treat 'em with respect - X10s are not the type of product that'll tolerate rough handling.
The X10s are also very light & comfortable (compared to Shures). If I wanted to be very picky, arguably the increment of the large earbuds to the mediums should be subtler - the step-up is more like med' to XL. Also, it would be useful if the 'L' & 'R' insignias were larger & bolder.
Now, when listening to music on my iPod Classic via in-ear headphones, the sound quality is no longer so 2nd-rate when compared to a home hifi setup. Sure, the X10s could never be described as 'modestly priced' but they're a classic example of YGWYPF.
(Don't bother upgrading to Comply T-100 foam earbud tips - the standard Klipsch 'gel' [aka rubber] earbuds produce superior sound & are more practical in day-to-day use, IMHO.)