I'm new to the world of IEMs (and smartphones, for that matter). I listen mostly to music from the 40's-50's: big bands, "The Great American Songbook." My main source is internet streaming radio — very compressed sound (unless I shell out $$ for Pandora One or Sky.fm premium). I have a recorded collection of this genre, too, ripped to AAC format. I also listen to contemporary a capella (Pentatonix, Rockapella, Nylons) regularly. There's also a small amount of classical music (chamber and orchestral), electric blues (BB King, Albert King, S.R. Vaughan, Chris Cain), and some guilty pleasures (70's pop, esp. Billy Joel).
My first IEMs were Apple Earpods, and I think they sound great on all the music I've listened to! The drawback is that I can't answer calls with them. I've tried some of the IEMs recommended on this site — Audio-technica Ath-ckm300is, Audio-technica Ath-chx5is Sonic Fuel, and SteelSeries Flux — and I've hated them all. They were either very uncomfortable or lacking in bass (for my tastes) with a thin-sounding mid-range. The only one that approached acceptable is the Sony MDR-EX100AP/L, but it's really "meh."
I've been looking around on this site for sub-$100 IEMs, but I really can't tell from reviews models are appropriate for my listening habits. It seems as if the new Xiaomi Piston 2.0 (w/ the HiFiMan RE400 filters and flanges mod), the Zero Audio carbo Tenore ZH-DX200-CT, or the Thinksound ts02 are good choices, but I've been disappointed with my review-based choices so far. Any other options more experienced IEM wearers can make would be much appreciated.