I've had a working Chromecast, with 13300 firmware including OTA. I just wanted to use the CC, but was confronted with a black screen. When a rebooted, I saw the logo from Team Eureka, which wasn't there before, so I Thought it was OTA updated (yes!). But the CC wouldn't boot completely, it left me with a black screen, I tried updating to 14975 manually, but that just gave me the same result; boot the device, Team Eureka logo blinking twice, and than the screen stays black.
To be able to use the CC, I have flashed the previous version of 13300 without the OTA. (And its working again) I will try updating again when there will be a new version.
I just thought I would share this information, if you like I can post a install log. Since nobody else is facing any issues, I guess it's just my luck