Just the usual issues with it not connecting, randomly disconnecting, audio buffering issues and so on. These usually get worse when you go into really busy places (the metro, train stations, shopping streets etc.)
When I lived in London I used to take Bluetooth-enthusiasts to a specific spot in Victoria station that is a complete Bluetooth-killer for some reason. Cables just don't have these problems ...
not OP, but in NYC, I cannot use my Airpods on the subway or while crossing an intersection. I tried commuting with them for a couple weeks, and as soon as I got into the subway my music would cut out.
Then out on the street, I would have no problems in the middle of a block, but on every intersection, the connection would cut out again until I got far enough from the corner.
Back to wired IEM's with a little dongle in the lightning slot :)
When I lived in London I used to take Bluetooth-enthusiasts to a specific spot in Victoria station that is a complete Bluetooth-killer for some reason. Cables just don't have these problems ...