The Nut: If you like high-end earbuds, give the Monster Turbine a look. They're surprisingly good for the price. But for most, something in the $30-50 range will do just fine.
High-end earbuds like those from Etymotic, Shure, or Ultimate Ears tend to use balanced armature drivers to produce sound, an old but reliable technology that centers the armature transducer directly inside a magnet, producing a considerable amount of sound without a lot of power—the low impedance is perfect for portable music players which don't have the luxury of power pouring limitlessly from the wall. Nicer earbuds might use more than one driver to produce different frequencies.
That's not what's inside the Monster Turbine earbuds. Instead, Monster has crammed a driver inside more typical of a bigger speaker—TK*. Hence the branding line "in-ear speakers".
The Monster Turbine earbuds do not sounds like in-ear speakers. I'm not even entirely sure what that would sound like; good headphones have a space to themselves, blasting right out of the pineal gland, but leaving the rest of the body relatively untouched. But they do sound extremely clean and crisp. Not miraculously so, but at least as nice as some models costing in the low hundreds. Bass is round but not overwhelming, although you might Considering that the Turbines sell for $150 and the most shocking thing about the Turbines becomes apparent: these may be a relative bargain from the same company that charges $60 for an HDMI cable.
They also look and feel ace. The metal feels good in the hand and ear (if they are perhaps a tad easy to pull out of the ear), there are a variety of silicone tips (no foam) to make a good shape in the ear (I had to snip the end off a tree to get it to stop tickling my ear canal, but that's no big deal; every ear is different), and the red and blue stripes that denote left or right are just understated enough.
The lack of a in-line microphone for iPhone, iPod Touch, or other standard three-line minijack connections is a real shame. For that reason alone I'd suggest phone users skip over the Turbines entirely.
Other folks seem to like them, too, with a few caveats: "Monster’s Turbine is the best dynamic based earphone I have heard when paired with Trance music, full stop" [Touch My Apps]
"In fact, the Turbine's bass, midrange, and treble tonal balance were remarkably consistent. And all this from headphones that cost half as much as the Etymotic and Klipsch headphones--the Turbine earphones definitely offer the best bang for the buck in this test group." [Steve Guttenberg]
"The Turbines are certainly attractive, with their serrated black chrome housings reminiscent of the back of an F-14 Tomcat." [Aric Annear]
"Is a hard-core audiophile going to love these - probably not." [Chip Chick]
"The Turbines impressed me because the highs snapped hard without any distortion, but the low-end just drops out." [Peter Ha]
* I've asked Monster exactly what they're using, but they haven't had time to respond yet. I'll add it back in later.