Macbook Pro 13 retina here and exactly the same issues and symptoms....
10.10.2 - bluetooth stuff worked like a dream..... 10.10.3 broken - stuttering mouse (unusable) keyboard continuously connected/disconnected and Bose mini soundlink squealing when outputting sound (when it manages to connect)...
I've SMC and PRAM reset, checked all the hardware etc.
On restart, everything works for about 20 seconds then the mouse problem appears......
Rolling back to 10.10.2 seems the only fix right now.
One thing that has not been fixed since Yosemite installation is the forced reload of Safari in order to kick start it into life.
All very very frustrating.
2 iMacs at work place are running Lion.... not upgrading to Yosemite in case the bluetooth peripherals break
I'm a long time apple customer, now very very frustrated