After updating to OS X 10.8.5, Bluetooth devices may stop responding. This is a fairly typical symptom reported with past OS X updates. Fixes include turning Bluetooth off then back on, zapping the PRAM, and resetting the SMC.

Apple has apparently dropped support for some very old Bluetooth based cellular devices, in particular ones that are Broadcom-based. If you use a Bluetooth device to connect to the internet via cellular, there’s a slight chance that updating to OS X 10.8.5 will break it. If this happens, you’ll need to get a replacement device from your provider.