Hi all, I am the guy whose post on the first page of this thread was voted the most. I have been watching this thread for some time now. I finally downloaded the 2/17/2016 update for my Surface Pro 4 (i5/8GB/256GB) today. In my first 2 hours of testing,
I have not encountered the "unable to wake from sleep" issue so far.
I have now set my surface to go to Sleep (instead of hibernate)
on closing the lid. The other settings such as power button are still set to hibernate. I will post back if I encounter the issue. Fingers crossed and good luck!

UPDATE:
I have continued to test it and determined that the "unable to wake from sleep"
issue is not fully resolved. In my case, it seems to be going to sleep and waking up fine as long as power supply is not involved.
But with power supply (I use Surface dock power cable, but no peripherals and no external monitors), I have been able to find a couple of
scenarios where it still fails to wake from sleep > 50% of the time.
Scenario 1: If Surface Pro 4 is disconnected from power supply and I close the lid, it goes to sleep per my "close the lid" setting. While it is sleeping, I connect the magnetic power supply cable. Now when I open the lid and try to wake
it up, the IR light and keyboard light up but Surface fails to wake up from sleep. I have to close the lid again to make it go to sleep mode in power supply "connected" mode. Then it wakes up on opening the lid and pressing a key/button.
Scenario 2: If Surface Pro 4 is connected to power supply cable and you close the lid (it goes to sleep) and then you disconnect the power supply cable and then open the lid and press a key, it won't wake up from sleep. The IR light and
keyboard light up but screen stays dark. I have to close the lid again to make it go to sleep mode in power supply "disconnected" mode. Then it wakes up on opening the lid and pressing a key/button.
So the bottom line is to try to wake it up in the same power supply cable connected or disconnected state that it went to sleep in. Otherwise, close and open the lid a second (or sometimes 3rd) time.
I will post more as I test more.
UPDATE#2
Closed the Surface Pro 4 lid, put it in the bag, left work and drove home. The Surface Pro 4 was very warm when I took it out after 40 minute drive. So I call the 2/17/2016 Surface Pro 4 update mostly useless for "sleep of death" issue.
I am going back to hibernate.