A LOUD, constant hissing and crackling noise when nothing's playing (also audible during podcasts or quiet music). Like 3x worse than my $40 truly wireless buds.
They are buggy. They would sometimes disconnect with no way to reconnect, requiring a factory reset (which you need the case to do).
It's too bad, in a lot of way's they're better than the AirPods. I prefer the "open audio" design to the transparency mode even, and they're more comfortable and secure in the ears.