I think many people who stick with the "OEM" earbuds only do, because they aren't aware of what's missing. I mean to myself, earbuds were earbuds, until I was looking for a way to block out ambient noise from mine. The Sonys I purchased had "sounded a little better" than my ipod buds - but not by much. (the only reason I got them was so they would stay in my ear - something OEMs couldn't do) FYI - they're technically considered "canal-phones" I believe. The difference between earbuds and canal phones / in ear monitors - is the seal that the later two achieve.
Now I look back wondering how it took me so long to realize it.