Who the hell checks their work at apple these days? I'm so pissed but luckily I was able to recover easily. Installed the 10.10.3 update via app store on my 2015 broad well 13" and waited for system to do it's thing. It finished then I started and see the white loading bar then it another restart and nothing - a blinking folder with question mark. Zapped PRam didn't do jack, so booted into recovery mode via command-R while powering on and selected startup disk and it worked. Really not happy with how apple QA's their updates these days!