my experience with sierra seems a bit better than with el capitan, but freezings still occur. I installed sierra on october, 14, i had three freezings since then (so on average one per week). The freezing behavior has changed: the os seems able to detect the freezing and logs you off, so you are shown the login page, you can put the pwd and continue to work. But you will find a crash log with this type of information
Process: WindowServer [172]
Path: /System/Library/PrivateFrameworks/SkyLight.framework/Versions/A/Resources/Windo wServer
Identifier: WindowServer
Version: 600.00 (13)
Code Type: X86-64 (Native)
Parent Process: launchd [1]
Responsible: WindowServer [172]
User ID: 88
Date/Time: 2016-11-04 18:56:13.111 +0100
OS Version: Mac OS X 10.12.1 (16B2555)
Report Version: 12
Anonymous UUID: 104B4B8B-1BF7-C820-8C67-6279D226F116
Sleep/Wake UUID: D8D1150F-16F8-4BD9-A650-D5E3E612EE49
Time Awake Since Boot: 19000 seconds
Time Since Wake: 2800 seconds
System Integrity Protection: enabled
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY
Application Specific Information:
Assertion failed: (false && "10 seconds of continuous GPU Driver unreadiness, relaunching WindowServer"), function void IMGGraphicsStackReadinessFailure(), file Server/Windows/Updater.cc, line 2860.
and something like this in your system.log
Nov 4 18:56:13 Mac-Pro-di-Mauro com.apple.xpc.launchd[1] (com.apple.WiFiVelocityAgent[
456]): Service exited with abnormal code: 143
Nov 4 18:56:13 Mac-Pro-di-Mauro com.apple.xpc.launchd[1] (com.apple.coreservices.useractivityd[396]): Service exited due to signal: Killed: 9 sent by useractivityd[396]
Nov 4 18:56:13 Mac-Pro-di-Mauro com.apple.xpc.launchd[1] (com.apple.ReportCrash.Root[759]): Endpoint has been activated through legacy launch(3) APIs. Please switch to XPC or bootstrap_check_in(): com.apple.ReportCrash.DirectoryService
Nov 4 18:56:13 Mac-Pro-di-Mauro com.apple.xpc.launchd[1] (com.apple.WiFiProxy[392]): Service exited due to signal: Killed: 9 sent by WiFiProxy[392]
Nov 4 18:56:13 Mac-Pro-di-Mauro ReportCrash[759]: assertion failed: 16B2555: libsystem_trace.dylib + 76912 [C029B910-A65F-35F6-B194-B933B454EAB4]: 0x0
Nov 4 18:56:13 --- last message repeated 2 times ---
Nov 4 18:56:13 Mac-Pro-di-Mauro com.apple.xpc.launchd[1] (com.apple.Dock.agent[310]): Service exited with abnormal code: 1
Nov 4 18:56:13 Mac-Pro-di-Mauro ReportCrash[759]: assertion failed: 16B2555: libsystem_trace.dylib + 76912 [C029B910-A65F-35F6-B194-B933B454EAB4]: 0x0