Experience the flaky bluetooth straight away after 10.9.1 update as well:
- was using apple wireless keyboard and trackpad
- updated Mac OS X to 10.9.1
- trackpad works after reboot, keyboard doesn't
- tried to pair the keyboard several times with no luck (it would be detected a few times but then pairing would not work; took out the batteries, restarted bluetooth on Mac etc.)
So far cannot use Apple Wireless Keyboard at all.
System specs:
- MacBook Pro 15 (late 2013)
Edit:
- after numerous tries to reconnect the keyboard I got to the stage where typing numbers and pressing enter was requested during pairin
- keyboard works again now (hope that lasts at least untill next system update)
Steps I did:
- took MacBook Pro away from everything together with Apple Wireless Keyboard
- turned of Bluetooth on Mac
- rebooted
- turned on/off bluetooth again
- went to System -> Keyboard -> Set Up Bluetooth Keyboard
- switched off keyboard, switched on (long press)
- keyboard was detected, pressed continue -> numbers to type appeared (typed them and pairing succeded)
The pairing would start many times and then stoped saying that keyboard is not detected. Eventually everything worked out. Have patience, perhaps it will work in your case too.
First time pairing Apple Wireless Keyboard on Mac OS X 10.9.0 was a breathe.