I have heard friends speak of bearing issues that come quickly. Other than that, I have not heard anything much. I like the Chris King sound of bees/buzz, and I can just about live with the DT 240 sound, but the sound of the I9s is a bit of torture. It kinda ruins the peaceful nature of most of my rides. I am sensitive to sounds though. I actually have a new American Classic wheelset (mainly bought t see how well their tubeless works) and those are some quiet hubs. I like that, though they likely will not last anywhere as long as a CK or DT hub.