Hi,
I had the same problem after upgrading a 2012 MacBook Air running Yosemite to Sierra.
I followed the instructions for resetting the PRAM (or NVRAM as it is referred to in the linked to article) and it seems to have worked for my problem. Please note that it did affect my sound after resetting it so I had to restart the MacBook a second time, then it has been fine since.
My symptoms were as others have described, the black screen when opening a closed MacBook; pressing the space bar or moving/clicking a trackpad that used to wake up the screen was no longer having an effect; pressing the on/off button was non-responsive and then after 30 seconds or so, things would start happening, almost like it had been storing up the button presses and clicks and then trying to action them when it finally got round to it.
My machine had always been very responsive to opening, or button presses and clicks after going to sleep through inactivity: Anywhere from 1 or 2 seconds up to around 10 at its rare but worst response times. It is now back to the almost instantaneous response that I have been used to.
As an aside, upgrading to Sierra seems to have improved my battery condition. Before upgrading my battery was reporting as requiring a service and would run down really quickly and sometimes turn off with lots of battery remaining without performing an emergency shutdown - sometimes causing data loss. Since the upgrade, it is performing much more consistently on battery and for longer. The message for battery service has gone and though battery operation time it is obviously much lower than at new, it will last an hour or two comfortably whereas previously, after 20 minutes on battery, the sweat would start to form on my forehead as an unexpected shout down could happen at any time.
I mention this because I originally thought my battery had packed in altogether when I was trying to wake up the MacBook and nothing was happening after pressing the power key; no lights or screen flickers were showing so I initially thought the MacBook was dead.