Just bought a pair of SE215s and been listening to them a couple of hours, mostly on public transport.
My initial impressions are:
Positive: Awesome isolation, very comfy, very full and deep bass.
Negative: Very warm sound, fluffy bass, SERIOUS lack of detail in the highs, general "veil" in upper mids.
This is based on just a couple of hours though, and compared directly to my Denon D2000s (listened to during the day in the office).
The Denons are more defined in the bass and have FAR more presence and detail in the upper mids and highs.
Don't know if it's a fair comparison, and these are my first IEMs. I bought them at a bargain, and my main objective was isolation for flying and PT. I think they fit the bill for that, but they are not audiophile to me.
That's kinda of an unfair comparison. 1. The SE215s are 2.5x cheaper. 2. Headphones are often known to offer better value for money, hence losing portability.