The sound quality is unusually good and neutral when they work. But they don't work very often.
The primary problem is that they unpair with each other (not with the phone -- the primary still usually kept connection to the phone) in lots of environments. Perhaps it has to do with ambient electronic interference. On my walk to work, they always unpaired leaving the train station, and again on the sidewalk in a 3-block span of my walk to the office from the train. At work, they would sometimes unpair while sitting at my desk, though if I didn't get up, they could remain paired all day.
Call quality was ok, but they only play a phone call through one bud, which makes conversations more difficult. Stereo call audio is very helpful, and these guys just made the wrong decision on that front.
They're comfortable, and I could leave them in my ears most of the day, which was great in a noisy office.
But the unreliable connection was such a nuisance and they were so likely to drop connection that I just stopped using them entirely. My search for a great pair of wireless buds goes on. Perhaps Erato will get these issues nailed down in a future product. (I did have them replace my buds, in case I just got a bad set. The replacement set was slightly worse in its tendency to drop connection, so it appears to be a design defect.)