Fully agree. X10s are so comfortable & tiny that they almost feel like an implant, without compromising sound quality or noise isolation. It's amazing how much bass such a miniature speaker can produce, when fitting properly.

Only disadvantage is that people don't realize you are wearing headphones and you don't hear them yelling at you.

Agreed, I love my S4s. They are the perfect in-ear headphones for the office and gym. Not to mention a great deal at ~$80.

I tried the Custom 2 and didn't like them at all. The right eartip wouldn't stay in my ear, the cords were easily damaged, and they were incredibly bright. I like a bright sound, but this was ridiculous.

I greatly prefer Etymotics.