Freesync has been unreliable/defunct for me and several other people on any Radeon driver version past and including 16.1. When playing most games, the display will erratically "drop out" of freesync mode, and revert to its default refresh rate for a short amount of time. On some games, this can happen so frequently that the monitor is hardly ever properly synchronized with the game's frame rate. The result is regular/constant tearing and, sometimes, severe judder to the point where using Freesync is detrimental to the overall experience. Installing Crimson software on top of an existing 15.11.1 driver installation does not break Freesync. Installing 16.1 or later does.
Complete failure of Freesync functionality can be provoked by using games/scenes with relatively high frame time variance as can be seen here (game: Grim Dawn, while causing a CPU limit) and here (Skyrim) both recorded with driver version 16.8.2 and with FRTC set to 50 FPS. Note the Monitor defaulting to 75hz as frame times diverge from the 20ms optimum at certain viewing angles/positions.
The following are a few videos by other users and setups demonstrating the broken freesync behavior with driver 16.1 onwards as opposed to the correct behavior up until version 15.11.1 on an otherwise unchanged system.
Version 16.1 to date:
Different person and hardware, same Issue:
16GB DDR4 2400mhz
MSI 390x @1080mhz -12mV