After a week I can provide the following observations with these in-ear headphones:
1. Sound Quality is excellent. Obviously, the bass response will depend on fit and seal, but even when not fully inserted, the headphones provided me with excellent separation, and more than adequate bass reponse.
2. Fitment will depend highly on the wearer. I have finnicky ears, and so I have needed to replace the cushions with a slightly smaller fit, hence my one star detraction for no other sizes being included with the package.
3. Durability so far has been good. With one exception of having a cushion pull away from the earpiece while they were rolling around in my duffle bag, these have stood up to the elements like champs. I have used them in wind and rain in my daily walk throughout the city, and have had no problems with ambient moisture affecting any of the contact points.
4. Functionality is exactly as advertised. These are no-frills phones, and as such they don't include any inline controls other than play/stop or mic activation. There are no controls for your player, just a one button nub for pausing music/muting the mic. However, I had no complaints regarding the quality of my mic. All of my phone calls came through with crystal clarity.
Bottom line, you can't go wrong for the few dollars these cost.