Pros: Good sound, forgiving sound signature, great isolation, detachable cable, you can use them as earplugs
Cons: Bass can get a bit annoying, highs are rolled-off
I've been a fan of Shure IEMs for a while. I had the E2c, E3c (two of them), and SE210 previously. Problem was the cable over-the-ear design. The cable going over the ear sucked in moisture, became hard and brittle, and finally broke. I wore my E3c like earbuds, which thankfully saved them from their demise and today they still live on, unlike the others. I was thrilled when I found out that the SE215 came with a detachable cable. Broken cable? Just replace the cable with another one. An excellent feature, especially for an entry level IEM.
There is a bit too much bass, though it's fun for electronic music. The treble roll-off gives an illusion of lack of detail, but also enables them to work well with badly recorded music or low bitrate files (like youtube videos). Midrange is very good, as is with all Shure products I've experienced. Over all the sound signature could be considered as warm.
I find these very comfortable. The medium black olives are the best for me. I can wear them all day, and sometimes I do.
Overall I like these quite a lot. Cheap, portable, isolate really well (I use them as earplugs in noisy situations), forgiving sound signature, great comfort, and detachable cable make these a winner for the price.