Hello, I've installed Sierra since the public beta on a friend's computer. It's a baseline rMBP 13" from 2015. Installation was done as an upgrade from El Capitan. He is currently experiencing massive issues with HDMI connectivity. It all started after the upgrade. PB1 was extreme crap, you needed to plug in the HDMI and hope for the best. The MB display would change resolution to that of the TV's, but on the TV you had few separate outcomes. - It would display normally after 2-3 minutes of blackness. The TV would be recognized successfully, even in sysprefs, but wouldn't display anything for few minutes. - It would start showing static on the TV and flicker like crazy. - It wouldn't work at all unless you rebooted the machine a few times. Ok. I thought these problems are normal, being the first public beta and being unstable and such. PB2 came along, but I wasn't there to witness it. He upgraded and told me everything worked just fine with HDMI then. I thought the bugs with the GPU have been fixed. PB3 came along. The problem came back, minus the "static" outcome. PB4 came along, and the HDMI would still be semi-broken. This time, instead of waiting few minutes for something to display on the TV, you would wait a few seconds and it worked fine after. I have no idea why this is so broken. I guess that's related to beta software, but we're near the final release and this still hasn't been fixed. Do you guys with 13" rMBPs from 2015 experience the same problem? Have you found a fix? What's to blame? I'm thinking GPU drivers, since it kernel panicked this week while working inside Safari on a GPU-heavy website. I will definitely clean install once the final version comes out. Disclaimer: Yes, I know this is a work machine and installing beta software is never an advice. The only reason I told him to install the PB is the new iCloud Drive features, which work wonderfully. So if you come into this thread to bitch how I shouldn't install beta software on work machines, please go away. I made this thread to see if others are affected by this problem. Thank you!