After a 10 hour wait for my OG PS4 backup to restore, I could finally start playing - I love it. Almost silent when a disc isn't inserted, and Ratchet & Clank looks absolutely incredible even at 1080p.
I had one worrying moment when starting Infamous Second Son, where it appeared the Pro tried to change video output on my TV for some reason - the screen went black and then said something along the lines of "Unsupported video source" or similar.
I thought no problem, I'll just restart, but the most worrying thing was the console would do nothing in this state. It was on, but the controller stopped responding, and pressing the power button on the Pro did nothing. Pressing eject made a beeping noise but didn't eject the disc. The controller also wouldn't connect via USB cable and just kept flashing as it does when it can't find the correct system to pair with.
In the end I had to power the console off at the wall, which I hate doing for obvious reasons, but there was no other way to restart it. Switched it back on, it checked the drive and all seems fine now, including Infamous.
Kinda worrying though. Hopefully just a one-off bug of some sort which won't happen again.