More thorough reviews of the sound can be found elsewhere (via Google). In short, you'll notice the similarity if you own a pair of Grado headphones, and if you don't, these are detailed, warm, exciting and dynamic.
Comfort: With the right ear tips, these will fit snugly and comfortably for hours. The best tips depend on your preferences and ears. Foam Comply tips are popular and compatible with these, but they have a limited life because the foam degrades. I'd recommend Sony hybrids. I suggest wearing them upside down, with the cable going over your ear and down. They never fall out, etc.
Durability: I've used these daily for 18 months and they're still working perfectly. They live in my pocket. The only minor issue I had was the rubber sleeving on the headphone jack becoming loose, but this was fixed by a drop of glue. The shape also adds to the durability, over some larger IEMs (e.g. models by Shure and Westone).
Overall: I've had more expensive headphones. In some areas they were better. Overall though, these are the best I've ever owned.