They have clean, very detailed sound, with good stereo separation. They're a touch bright (the treble has an ever-so-slight harsh edge) but overall they have a flat, balanced profile and work well with a variety of music. However, they just don't produce big, thumping bass, so they're going to be less desirable to folks who listen to a lot of hip-hop and techno.
For instance, on Swedish House Mafia's track "Don't You Worry Child," the lead vocalist's voice really jumps out at you -- he's very immediate and clear. But when the bass line kicks in, it feels a bit restrained. It's there, but lacks the big punch.
In short, if you if you like clean, detailed, and fairly accurate headphones, the Keramos should appeal to you. But bass lovers will probably be a little disappointed.
I liked Moshi's Keramo in-ear headphones, though they're clearly not for everybody. They have a stylish, polished look, their ceramic design seems quite sturdy, and they're pretty fairly priced at $120 (they'd be a deal at $99, however). They also come with a nice carrying case and an inline remote and microphone for making cell phone calls.
For in-ear headphones they're pretty comfortable, though I think that due to their slightly larger size they'd fit folks with bigger ears a little better.
While I've said that bass lovers may be disappointed, that doesn't mean the Moshi Keramo headphones lack bass. It's just so many headphones and earphones these days boost the bass, so listeners have gotten used to bigger, boomier bass. The Keramos, in contrast, have a flatter profile and it's their detail, not their bass, that's more likely to jump out at you.