After using the SE215s for just over 3 years, I think I can give a fair judgement now. They are used during running (also during rain), riding motorcycle, in the bus, at university/work, behind PC. Pretty much all imaginable scenarios.
In these scenarios I have found all other headphones I used lacking in either: sound quality, durability (especially near the jack-plug and being semi-waterproof) and/or flimsy cord.
So far the SE215s have suited me reasonably well.
What I like:
-They seat very well, only headphones that I can go running with without them falling out.
-Excellent music quality for the price and form factor.
-Reasonably waterproof due to the tight fit.
-Durable cord that isn't prone to breaking.
What I dont like:
-The connectors between the earphones and cord are very prone to wear, and non-replaceable. This is a known issue for Sure but they dont fix it. If I had the option I'd rather buy these headphones with fixed cords instead of this point of failure. For me this happened about 2 to 2.5 years after use.
The only thing holding back 5 stars for me are the connectors that are very prone to wear and dirt.