It seems like quite a few people are having trouble with the screen waking up since upgrading to Sierra (see the links below). I have a relatively new iMac (2015 5K) which was rock solid on El Capitan but since upgrading to Sierra I find that almost every day I have to power cycle due to the screen failing to wake up from sleep. I hit the keys but nothing happens. I know the machine is still on because I can feel the air being pushed through the vents by the fan and the log file entries show that processes are still active while the machine remains unresponsive. Sometimes it wakes up but takes much longer to respond than it ever did on El Capitan (e.g. 5-10 secs). I never had any issues on 10.11 and this has really spoilt my experience. I was getting a lot of joy out of this new iMac until Sierra messed things up! I have very little 3rd party s/w installed on the machine so far, apart from Office, Spotify, the various cloud sync tools and some small-footprint third party helper tools and diagnostics (Hazel, Alfred, EtreCheck) which have always been rock solid on any Mac I've owned. As quite a few others seem to be getting hit by this issue using various H/W i've collated some links to other people's posts about it. Maybe it's time to make a sticky? :-0 http://forums.macrumors.com/threads...rty-nvram-or-smc-issue.2003314/#post-23649178 http://forums.macrumors.com/threads...rom-sleep-after-macos-sierra-upgrade.2002216/ http://forums.macrumors.com/threads...from-sleep-external-monitor-is-green.2002427/ http://forums.macrumors.com/threads/sierra-mac-book-air-mid-2011-waking-up-slower.2001431/ http://forums.macrumors.com/threads/os-sierra-hard-to-wake-up.2003308/ --- Post Merged, Oct 2, 2016 --- One other thing I've noticed - the trackpad (1st gen) always loses connection after a restart. Again, this seems to something that only started since Sierra. I also have the Magic Keyboard and Mouse and they don't have issues. I've just done an SMC reset so I'll report back later as to whether that has helped.