I've been unable to make a (x86_64) build using the most recent beta version of Unity 5.4 due to these errors:
GetBool is not allowed to be called from a MonoBehaviour constructor, call it in Awake or Start instead. Called from script 'PlayMakerWelcomeWindow' on game object ''.
See "Script Serialization" page in the Unity Manual for further details.
UnityEditor.EditorPrefs:GetBool(String, Boolean)
HutongGames.PlayMakerEditor.PlayMakerWelcomeWindow:.cctor() (at Assets/PlayMaker/Editor/PlayMakerWelcomeWindow.cs:97)
SetLogCallbackDefined is not allowed to be called during serialization, call it from Awake or Start instead. Called from script 'FsmEditorWindow' on game object ''.
See "Script Serialization" page in the Unity Manual for further details.
UnityEngine.Application:add_logMessageReceived(LogCallback)
HutongGames.PlayMakerEditor.FsmDebugger:.ctor() (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/FsmDebugger.cs:51)
HutongGames.PlayMakerEditor.FsmDebugger:.cctor() (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/FsmDebugger.cs:22)