Android Marshmallow Release Delays
You can count on some delays.
We've never seen a Samsung Android release that didn't get impacted, in some way, by testing delays behind the scenes. Updates often fail in testing and that forces Samsung, or the carrier, to go back to the drawing board and correct the mistakes.
We expect to see Android 6.0.1 Marshmallow delays. You won't know about all of them though because only a small portion of carriers actually communicate these things to their customers.