CoreBluetooth delegates on main queue/main thread?
the point of async callbacks is that they dont need to be scheduled because they get called when the heavy-work is over... of course when your delegate methods are heavy, this doesnt work anymore and it does make sense to move them to a different queue :)
OR if they are called 10000 times per secon. but apart from that, I dont think they need to be moved out of the main queue
Depending on how you are using CoreBluetooth, there may arrive a lot of callbacks per second, hence I strongly advise creating a dedicated (serial) dispatch queue to handle them in coordinated fashion.