I've upgraded two sites to 8.3.0 from 8.2.7. This log is from the last one:
[05-Apr-2017 19:06:56 America/Los_Angeles] PHP Fatal error: Call to a member function get() on array in /home/radixcod/public_html/sensarium.com/core/lib/Drupal/Core/Cache/CacheCollector.php on line 327
[05-Apr-2017 19:07:01 America/Los_Angeles] PHP Fatal error: Call to a member function get() on array in /home/radixcod/public_html/sensarium.com/core/lib/Drupal/Core/Cache/CacheCollector.php on line 327
[05-Apr-2017 19:07:07 America/Los_Angeles] PHP Fatal error: Call to a member function get() on array in /home/radixcod/public_html/sensarium.com/core/lib/Drupal/Core/Cache/CacheCollector.php on line 327
[06-Apr-2017 02:07:36 UTC] PHP Fatal error: Call to a member function get() on array in /home/radixcod/public_html/sensarium.com/core/lib/Drupal/Core/Cache/CacheCollector.php on line 327
[05-Apr-2017 19:07:37 America/Los_Angeles] PHP Fatal error: Call to a member function get() on array in /home/radixcod/public_html/sensarium.com/core/lib/Drupal/Core/Cache/CacheCollector.php on line 327