Plenty of fear mongering going around.
Will some folks have issues? Of course.
Will most not have issues? Certainly. They just don’t pipe up and say how everything is working as expected.
Do your homework (as others have suggested) and see what apps you might lose with the move to 64bit apps.
@dan and @Tom say 8.4 is good to go! @isaiah has provided an update on his products. Other plugins, check with the devs.
Party on, Garth!