I've had the headphones since January, I use them daily for about 3 continuous hours and for their price (I see them now for around 20 euros on Skroutz, I bought them a bit cheaper) they are perfect with amazing, deep, stereo sound and with flawless bass, and during calls, you can hear and be heard perfectly by the person on the other end.
It might just be my pair, but they have a slight hassle - a process to get both to produce sound simultaneously; they need to be placed in the charging case at the same time and taken out simultaneously, otherwise, the sound doesn't sync between the two. But really, in light of all their positives in relation to their cost, this is just a drop in the ocean, even though at times it can be quite annoying, especially if you're in a hurry to take a call, etc.