They hurt after only 20 min. This is subjective and they may fit perfectly for some however it's a fault when there is no solution to size for other people ( e.g., different size foam covers, etc)
you can't wear glasses with them. For an activity based device you are likely outdoors wearing sunglasses when you run or bicycle.phone and any audio alert through the headphones is an order of magnitude quieter and you can barely hear it. Also voice quality is poor for when you are talking on the phone too. Was confirmed by all people I called. They could barely hear me.
I really wanted these to work as the form factor is great and they are simple to use.